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# Logic's puzzle

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Little logic's puzzle for whoever is interested,

You are on a quest from Proqzanthar to Krighontyr but find a T-crossing and don't know which way to go.
At the T-crossing there are two twin brothers of which one is always true and the other is always false, but you don't know which one is which.
You can ask only one question to one of the two brothers.
Which question should you ask if you want to know whether to go left or right?
reinout-g  Jan 29, 2014

#4
+11
theiswe:

You can ask either of the twins the following question: "Which way would the other twin tell me to go?" and then you go the opposite direction!

Lets say Left is the correct way, and right is the wrong way.
If you ask the truthful twin (A) which way the other twin (B) would tell you to go, twin A will tell you that twin B would say "Right".
If you ask the lying twin (B) which way the other twin (B) would tell you to go, twin B will tell you that twin A would say "Right".
Therefore you should go the opposite way of what either of the twin replies to your question

Correction: If you ask the lying twin (B) which way the other twin (A) would tell you to go, twin B will tell you that twin A would say "Right".

Could not edit my previous post,thus a new post to correct myself.
Guest Jan 29, 2014
Sort:

#1
+91469
+8
reinout-g:

Little logic's puzzle for whoever is interested,

You are on a quest from Proqzanthar to Krighontyr but find a T-crossing and don't know which way to go.
At the T-crossing there are two twin brothers of which one is always true and the other is always false, but you don't know which one is which.
You can ask only 1 question to either of the two brothers.
Which question do you need to ask to know whether to go left or right?

I am not sure that I understand the question.
If I can ask 1 brother 1 question and then ask the other brother a different question then I know how to do it.
Is this what you meant?
Melody  Jan 29, 2014
#2
+2353
+8
Melody:
reinout-g:

Little logic's puzzle for whoever is interested,

You are on a quest from Proqzanthar to Krighontyr but find a T-crossing and don't know which way to go.
At the T-crossing there are two twin brothers of which one is always true and the other is always false, but you don't know which one is which.
You can ask only 1 question to either of the two brothers.
Which question do you need to ask to know whether to go left or right?

I am not sure that I understand the question.
If I can ask 1 brother 1 question and then ask the other brother a different question then I know how to do it.
Is this what you meant?

I edited it, Does that make it more understandable? So in total you can ask only 1 question and you have to pick one of the two brothers.
reinout-g  Jan 29, 2014
#3
+11
You can ask either of the twins the following question: "Which way would the other twin tell me to go?" and then you go the opposite direction!

Lets say Left is the correct way, and right is the wrong way.
If you ask the truthful twin (A) which way the other twin (B) would tell you to go, twin A will tell you that twin B would say "Right".
If you ask the lying twin (B) which way the other twin (B) would tell you to go, twin B will tell you that twin A would say "Right".
Therefore you should go the opposite way of what either of the twin replies to your question
Guest Jan 29, 2014
#4
+11
theiswe:

You can ask either of the twins the following question: "Which way would the other twin tell me to go?" and then you go the opposite direction!

Lets say Left is the correct way, and right is the wrong way.
If you ask the truthful twin (A) which way the other twin (B) would tell you to go, twin A will tell you that twin B would say "Right".
If you ask the lying twin (B) which way the other twin (B) would tell you to go, twin B will tell you that twin A would say "Right".
Therefore you should go the opposite way of what either of the twin replies to your question

Correction: If you ask the lying twin (B) which way the other twin (A) would tell you to go, twin B will tell you that twin A would say "Right".

Could not edit my previous post,thus a new post to correct myself.
Guest Jan 29, 2014
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Stumbled upon this article describing (and solving) the what is claimed to be 'hardest logic's puzzle ever'.

It is for the real logic's puzzle fanatics only and I suggest you do not try to solve it yourself since it is indeed extremely hard to crack.

http://www.thebigquestions.com/boolos.pdf
reinout-g  Feb 7, 2014
#6
+91469
+8
bump
Melody  Feb 9, 2014
#7
+37
+8
I believe I've got it.

You ask either of the brothers how the other brother would tell you to get to Krighontyr from the T crossing. Then you go the opposite direction.

Let's say that the correct path is R and you pick the false one to question.

The false brother knows that the true brother would say R, so he would say L, lying about the answer.

If by chance you got the true brother, then he would say L, too because he knows that the false brother would lie about the correct answer.

Either way you get the same answer and know that it's false; you must go the other way to Krighontyr!

This works regardless of what the true path is or who you ask because you'll always end up with a false answer.

That was fun.
Grammar Fascist  Feb 13, 2014
#8
+91469
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Ok Grammar Fascist, very well done,

Now you can try the new one that Reinout-g has presented

http://www.thebigquestions.com/boolos.pdf

That should keep you busy for a while.
Melody  Feb 13, 2014
#9
+37
+8
Yeah...not even going to try that one. I have other things I must dwell on. Sorry I haven't been able to assist in answering anything today; Tuesdays and Thursdays are especially busy for me. I'll try to help tomorrow, but no promises! I'm a busy man....I do enjoy helping people out, though!
Grammar Fascist  Feb 14, 2014
#10
+91469
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Grammar Fascist:

Yeah...not even going to try that one. I have other things I must dwell on. Sorry I haven't been able to assist in answering anything today; Tuesdays and Thursdays are especially busy for me. I'll try to help tomorrow, but no promises! I'm a busy man....I do enjoy helping people out, though!

That's fine, come when you can, we like having you here.
Melody.
Melody  Feb 14, 2014
#11
+2353
+5
New puzzle!

Three rivalling coaches (Pierre, Pieter and Peter) and their three athletes (Édouard, Eduard and Edward) want to cross a river.

There is only one boat which can carry two persons.

The coaches do not want other coaches to be with their athlete without they themselves beeing present at any moment..

How can they cross the river?
reinout-g  Mar 2, 2014
#12
0
If you ask one borther if you were the other brother which way should i go,
if he tells the truth then he would point the wrong way
if he tells a lie he would also point the wrong way

so go in the direction where the brothers don't point to
Guest Mar 3, 2014
#13
+91469
+5
reinout-g:

New puzzle!
Three rivalling trainers (Pierre, Pieter and Peter) and their three athletes (Édouard, Eduard and Edward) want to cross a river.
There is only one boat which can carry two persons.
The trainers do not want other coaches to sit with their athlete.
How can they cross the river?

Firstly, i can't handle all those Ps and Es
Mine are going to be Cs and As

We have
C1, A1, C2, A2, C3, A3 to get across the river
first C1 and A1 paddle across the river C1 stays

A1, C2, A2, C3, A3
Now C2 and A2 paddle across the river C1 and C2 stay

A1, A2, C3, A3
Now C3 and A3 paddle across the river C1, C2 and C3 stay

A1, A2, A3
Now A1 and A2 paddle across the river C1, C2, C3, A1 stay

A2, A3
Now A2 and A3 paddle acrosst the river and they are all safely on the other side.
Melody  Mar 4, 2014
#14
+2353
+5
Melody:
reinout-g:

New puzzle!
Three rivalling coaches (Pierre, Pieter and Peter) and their three athletes (Édouard, Eduard and Edward) want to cross a river.
There is only one boat which can carry two persons.
The coaches do not want other coaches to sit with their athlete.
How can they cross the river?

Firstly, i can't handle all those Ps and Es
Mine are going to be Cs and As

We have
C1, A1, C2, A2, C3, A3 to get across the river
first C1 and A1 paddle across the river C1 stays

A1, C2, A2, C3, A3
Now C2 and A2 paddle across the river C1 and C2 stay

A1, A2, C3, A3
Now C3 and A3 paddle across the river C1, C2 and C3 stay

A1, A2, A3
Now A1 and A2 paddle across the river C1, C2, C3, A1 stay

A2, A3
Now A2 and A3 paddle acrosst the river and they are all safely on the other side.

I'm sorry Melody, I think I've been to vague in my description ( I will edit it after this reply)

What I meant was that the coaches dont want their athletes to be near another coach without them beeing present at any moment.

In your solution, After A1 paddles back, he is alone with both C 2 and 3.
reinout-g  Mar 4, 2014
#15
+91469
0
reinout-g:

New puzzle!
Three rivalling coaches (Pierre, Pieter and Peter) and their three athletes (Édouard, Eduard and Edward) want to cross a river.
There is only one boat which can carry two persons.
The coaches do not want other coaches to be with their athlete without they themselves beeing present at any moment..
How can they cross the river?

Firstly, i can't handle all those Ps and Es
Mine are going to be Cs and As

We have A1, C1, A2, C2, A3, C3 to get across the river
A1 and C1 paddle across and A1 stays

We have C1, A2, C2, A3, C3 to get across the river
A2 and C2 paddle across and A1, A2 stay

We have C1, C2, A3, C3 to get across the river
A3 and C3 paddle across and A1,A2 and A3 stays

We have C1, C2, C3 to get across the river
C1 and C2 paddle across and A1, C1, A2, C2 stay A3 returns (he doesn't talk to anyone first - is that alright?)

C3 and A3 paddle across and then they are all there.

Is that okay or is there a better answer?

NO WE HAVE TO SCRAP THIS ONE IT DOESN'T FOLLOW THE RULES - SORRY.
Melody  Mar 5, 2014
#16
+2353
+5
Melody:
reinout-g:

New puzzle!
Three rivalling coaches (Pierre, Pieter and Peter) and their three athletes (Édouard, Eduard and Edward) want to cross a river.
There is only one boat which can carry two persons.
The coaches do not want other coaches to be with their athlete without they themselves beeing present at any moment..
How can they cross the river?

Firstly, i can't handle all those Ps and Es
Mine are going to be Cs and As

We have A1, C1, A2, C2, A3, C3 to get across the river
A1 and C1 paddle across and A1 stays

We have C1, A2, C2, A3, C3 to get across the river
A2 and C2 paddle across and A1, A2 stay

We have C1, C2, A3, C3 to get across the river
A3 and C3 paddle across and A1,A2 and A3 stays

We have C1, C2, C3 to get across the river
C1 and C2 paddle across and A1, C1, A2, C2 stay A3 returns (he doesn't talk to anyone first - is that alright?)

C3 and A3 paddle across and then they are all there.

Is that okay or is there a better answer?

NO WE HAVE TO SCRAP THIS ONE IT DOESN'T FOLLOW THE RULES - SORRY.

You're on the right track,

try again
reinout-g  Mar 5, 2014
#17
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reinout-g wrote:New puzzle!
Three rivalling coaches (Pierre, Pieter and Peter) and their three athletes (Édouard, Eduard and Edward) want to cross a river.
There is only one boat which can carry two persons.
The coaches do not want other coaches to be with their athlete without they themselves beeing present at any moment..
How can they cross the river?

Same as before. We have three coaches C1, C2, and C3
and we have 3 athletes A1, A2, A3

So A1, A2, A3, C1, C2, C3 all have to get accross the river
A1, and C1 paddle across and A1 stays on the other side (C1 returns)

So A2, A3, C1, C2, C3 all have to get accross the river
C1, and C2 paddle across and A1 AND C1 stays on the other side (C2 returns)

So A2, A3, C2, C3 all have to get accross the river
C2, and C3 paddle across and C1, C2 and C3 stays on the other side (A1 returns)

So A1, A2, A3, all have to get accross the river
A1, and A2 paddle across and A1, C1, C2 and C3 stays on the other side (A2 returns)

So A2, A3, all have to get accross the river
A2, and A3 paddle across and everyone is on the other side
Melody  Mar 12, 2014
#18
+2353
+5
Melody:

reinout-g wrote:New puzzle!
Three rivalling coaches (Pierre, Pieter and Peter) and their three athletes (Édouard, Eduard and Edward) want to cross a river.
There is only one boat which can carry two persons.
The coaches do not want other coaches to be with their athlete without they themselves beeing present at any moment..
How can they cross the river?

Same as before. We have three coaches C1, C2, and C3
and we have 3 athletes A1, A2, A3

So A1, A2, A3, C1, C2, C3 all have to get accross the river
A1, and C1 paddle across and A1 stays on the other side (C1 returns)

So A2, A3, C1, C2, C3 all have to get accross the river
C1, and C2 paddle across and A1 AND C1 stays on the other side (C2 returns)

So A2, A3, C2, C3 all have to get accross the river
C2, and C3 paddle across and C1, C2 and C3 stays on the other side (A1 returns)

So A1, A2, A3, all have to get accross the river
A1, and A2 paddle across and A1, C1, C2 and C3 stays on the other side (A2 returns)

So A2, A3, all have to get accross the river
A2, and A3 paddle across and everyone is on the other side

C2 paddles back and forth during move 2 leaving A2 behind with C3

Hope I did not disappoint you to much
reinout-g  Mar 12, 2014
#19
0

"which is the way from Krighontyr to Proqzanthar?" this is the reverse question i'm in proqzanthar heading to krighontyr so ofcourse i am adverese to the wa of proqzanthar. then depending on each twin's answer i'll know which path to take. if its the true twin he would point the exact direction from each place and if its the false twin he would point the opposite direction but since i know proqzanthar then i know which path to take.
Guest Mar 12, 2014
#20
+91469
0
Well, arn't you the clever/lucky one
Melody.
Melody  Mar 12, 2014
#21
+142
0
reinout-g:

New puzzle!

Three rivalling coaches (Pierre(A1), Pieter(B1) and Peter(C1)) and their three athletes (Édouard(A2), Eduard(B2) and Edward(C2)) want to cross a river.)

There is only one boat which can carry two persons.

The coaches do not want other coaches to be with their athlete without they themselves beeing present at any moment..

How can they cross the river?

A1 A2 cross the river, A1 came back.

A1 B1 cross the river, B1 came back.

B1 B2 cross the river, B1 came back.

B1 C1 cross the river, C1 came back.

C1 C2 cross the river, the end.
samgelinas  Mar 12, 2014
#23
0
and their three athletes (Édouard, Eduard and
Edward)

First édouard and eduard enter the boat to the other side, eduard drops off and édouard paddles back and picks up pierre. Édouard drops at the other side and pierre paddles back and picks up pieter. They both drop off at the other side. Édouard paddles back again and picks up edward. Édouard drops off at the other side and edward paddles back and picks up peter. They both drop off at the other side.

In essence no athelete is left in th presence of another coach without his coach being present.
Guest Mar 12, 2014
#24
+2353
+5

A1 A2 cross the river, A1 came back.

A1 B1 cross the river, B1 came back.

B1 B2 cross the river, B1 came back.

B1 C1 cross the river, C1 came back.

C1 C2 cross the river, the end.

in step two, B1 is in the presence of coach A2

reinout-g  Apr 13, 2014
#25
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0

and their three athletes (Édouard, Eduard and
Edward)

First édouard and eduard enter the boat to the other side, eduard drops off and édouard paddles back and picks up pierre. Édouard drops at the other side and pierre paddles back and picks up pieter. They both drop off at the other side. Édouard paddles back again and picks up edward. Édouard drops off at the other side and edward paddles back and picks up peter. They both drop off at the other side.

In essence no athelete is left in th presence of another coach without his coach being present.

Pierre is shortly in the presence of Eduard when he drops of éduoard. Therefore, your answer is incorrect

reinout-g  Apr 13, 2014
#26
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0

the only question you need to ask is if they like one direction whoever says yes is the brother that tells the truth whoever says no is a liar if neither then lick their hair :)

bioschip  Apr 18, 2014
#27
+10

You ask one brother what the other one would say, and then go the opposite, because if they are lying you go the opposite of what they tell you and if they are telling the truth about what the other would say then you would still go the other way. BOOM

Guest Apr 20, 2014
#28
+10

You ask one brother what the other brother will tell you is the correct way, then go the opposite way.

If you ask the truthful brother, he will respond with what the lying brother says, which would be the wrong way.

If you ask the lying brother he will lie about which path the truthful brother would say- so either way you go the opposite of what they say.

Guest Apr 26, 2014
#29
+14
+5

I got easy way! Go and get a GPS!

Edison  May 1, 2014
#30
+14
+5

Ask a Random child,if he say this way, say “ are you sure "

“promise ok?”

if you lie,your nose will be long!”

“I'm telling the truth,when you lie your nose will be long"

He might sound scare and that me he is telling the lie!

Edison  May 1, 2014
#31
+10

C=coach A= athelete

C1A1, C2A2 C3A3 start off the same side. A2 crosses with A1. A2 returns but leaves A1. Boat is with the starting side. C1, C2A2, C3A3((RIVER)) A1

A2 crosses with A3, leaves A3, and returns. Boat is on the starting side and A1 and A3 have crossed.

Now the arrangement is C3 C2A2 C1((RIVER)) A1, A3. The boat is with the coaches.

C3 and C1 cross. Now just C2 A2 remains. C2A2 ((RIVER)) C3A3 C1A1. However, the boat is with C1A1's side.

C1A1 returns with the boat, so now it is C2A2 C1A1 ((RIVER)) C3A3. Boat with C1A1's side.

C1 and C2 cross. Now it is A2, A1 ((RIVER)) C3A3, C2, C1. Boat on C1 and C2's side.

A3 crosses. A2,A1,A3((RIVER))C3,C2,C1. Boat is with A3's side.

A2 and A3 cross. Now it is A1((RIVER))C3A3, C2A2, C1. Boat with C1's side.

C1 crosses. Now: A1C1 ((RIVER)) C3A3, C2A2. Boat with A1C1's side. A1C1 Cross, YAHOO!

Guest May 6, 2014
#32
+2353
+5

Nice job Anonymous!

You are the very first one to correctly answer the coaches, athletes problem!

Reinout

reinout-g  May 7, 2014
#33
+2353
+5

It is time for a new logic puzzle!!

It took me a while to solve this one, but eventually I found the answer.

There's a street with 5 houses with 5 different colors in a row. Each house has a owner with a different nationality, each owner drinks a certain type of beverage, smokes a certain brand of cigar and has a certain pet. All owners have a different pet, type of cigar or drink. There are 15 hints given:

1. The Brit lives in the red house.
2. The Swede keeps dogs as pets.
3. The Dane drinks tea.
4. The green house is on the immediate left of the white house.
5. The green house's owner drinks coffee.
6. The owner who smokes Pall Mall rears birds.
7. The owner of the yellow house smokes Dunhill.
8. The owner living in the center house drinks milk.
9. The Norwegian lives in the first house.
10. The owner who smokes Blends lives next to the one who keeps cats.
11. The owner who keeps the horse lives next to the one who smokes Dunhill.
12. The owner who smokes Bluemasters drinks beer.
13. The German smokes Prince.
14. The Norwegian lives next to the blue house.
15. The owner who smokes Blends lives next to the one who drinks water.

Find out who owns the fish...

Reinout

reinout-g  May 14, 2014
#34
+2353
0

bump bump bump

reinout-g  May 15, 2014
#35
+5

The German owns the fish.

 Nationality Norwegian Dane Brit. German Swede. Drink Water Tea Milk ???? Beer Cigar Dunhill Blends Pall Mall Coffee Bluemaster Pet Cats Horses Birds Prince Dogs Color of House Yellow Blue Red Green White
Guest May 16, 2014
#36
+2353
+5

Well done anonymous!

Do you have a registered account, so I can see who's the genius behind the answer?

If you don't please do... It takes little time and makes us able to identify you on the forum.

Reinout

reinout-g  May 19, 2014
#37
0

Believe me, I would join but the terms of agreement still don't set right with me. Thankyou for the invite but I have to decline.

Guest May 19, 2014
#38
+91469
0

Hi Anonymous,

If you are a conscientious objector we can respect that.

If you post a lot why don't you give yourself a unofficial username - you can put it at the end of all your posts and we will slowly learn who you are.

We would really like you to be a proper 'member' of the forum even if it is unofficial.

Melody  May 21, 2014
#39
+2353
0

Could you elaborate on what you find unsettling in the terms of agreement?

reinout-g  May 22, 2014
#40
+18
0

I would say the false is is the dumb one

Kalecia  May 22, 2014
#41
+3

"If I asked the other one which way not to go, what would he say?" Then you go that way.

Guest May 30, 2014
#42
+3

you would ask a question to one twin that you knew the correct answer to and if the twin got the right answer that was the one that always told the truth so you ask his brother which way to go and he would tell a lie so if you needed to go right he would say left so you would know to go right.

Or, the brother that always told a lie would answer the first question which means he would get the answer incorrect. so you would know that the other brother always told the truth. so if he told you to go right you would know to go right and if he told you to go left you would know to go left.

Guest Jun 26, 2014
#43
+6

I would ask the brothers if the ground is dirt. If a brother says no, then he is lying and I shouldn't go his way.

Guest Jun 28, 2014
#44
+91469
+8

But he hasn't given you a 'way' and you have used your question up.

Melody  Jun 28, 2014
#45
+8256
0

So confusing. You have good questions, or puzzles. Really good question. May you please give me a hint?

DragonSlayer554  Jul 9, 2014
#46
+271
0

Wait! This game is is a bit like the Chinese card game number 24 except the magic number doesn't change!

Pyramid  Oct 18, 2014
#47
+91469
0

Which game are you talking about Pyramid?

Melody  Oct 18, 2014
#48
+271
0

Whoops. I was meant to post this in "Number Puzzle"

Pyramid  Nov 19, 2014
#49
+91469
0

Logic Puzzle      (thanks flflvm97)     17/12/14

http://web2.0calc.com/questions/flflvm-s-daily-question-day-4

Boat puzzle.   Thanks Daisy  (18/12/14)

http://web2.0calc.com/questions/a-farmer-needs-to-ring-a-wolf-a-goat-and-a-cabbage-across-the-river-in-a-boat-the-boat-is-tiny-and-canonly-carry-one-passenger-at-a-time-be

Gambling Puzzle   Thanks anon and Geno3141      (22/12/14)

I think this is a repeat puzzle but it is a good one.

http://web2.0calc.com/questions/here-is-a-riddle-that-i-ve-heard-long-time-ago

Melody  Dec 16, 2014
#50
+91469
0

A little money logic from CPhill     (23/1/15)

http://web2.0calc.com/questions/7-11

difficult number selections.  Great logic from Bertie and Alan       (6/3/15)

The Monty Hall Problem    -   Three doors, one prize       (17/3/15)

http://web2.0calc.com/questions/the-monty-hall-problem

Lockers problem     27/3/15

http://web2.0calc.com/questions/frustrating-brain-teasers

How slow is my clock      5/5/15

Where can the spies sit?   Thans MathsGod1    10/5/15

http://web2.0calc.com/questions/tricky-maths-question

When is Cheryl's Birthday?    12/5/15

http://web2.0calc.com/questions/logic-a-math-olympics-question

How many children did mum have?  14/5/15

http://web2.0calc.com/questions/how-many-children-were-you

How long did she walk for?      29/5/15

http://web2.0calc.com/questions/a-chauffeur-always-arrives-at-the-train-station-at-exactly-five-o-clock-to-pick-up-his-boss-and-drive-her-home-one-day-his-boss-arrives-an

Determine the number     29/5/15

http://web2.0calc.com/questions/write-a-ten-digit-number-so-that-the-first-digit-tells-how-many-zeros-there-are-in-the-number-the-second-how-many-ones-the-third-how-many

To to get 4 L with only a 3L and 5 L container         31/5/15

http://web2.0calc.com/questions/a-recipe-calls-for-4-cups-of-water-you-have-only-a-3-cup-and-a-5-cup-container-how-can-you-measure-out-four-cups-of-water

Melody  Jan 22, 2015
#50
0

What would the other person say

Guest Sep 3, 2015
#51
+600
0

Beats me.

Eloise1st  Sep 19, 2015
#52
+2592
0

I have not looked at the solution whilst writing this.

http://www.thebigquestions.com/boolos.pdf\

The puzzle:

I looked at this for 15 mins before giving up and looking.

Puzzle 1: Point to leftmost card and ask "Is there an ace to right of this card?"

This would only work if the jack isn't the middle.

Other that that, I'm stumped..(only thought on it for 10 minutes)

Puzzle 2: "What would the other god tell me?"-Taken from the twins puzzle

Puzzle 3: "If ja means yes, is Dushanbe in Kirghizia?"

SpawnofAngel  Jan 29, 2016
#53
+799
0

Ask which way the other brother would say, and then go the other way!

Landry  Mar 30, 2016

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