You received another calculator gift over the holidays. It has only two keys: a +1 key and a x5 key. The number 1 appears on your display. Describe a sequence of eleven key punches that you can use to make the year 2020 appear on the display?
work backwards from 2020
remember if you go backwards then you can -1 and divide by 5
It falls out easily.
Once you can do it backwards you can then reverse everything and do it forwards.
Please no one provide a fuller answer. Guest needs to do some thinking on his/her own.