Determine the four-digit natural numbers of the form abcd with property (a-1)(b-2)(c-3)(d+2019)=2020.
I found 2 such numbers:
2121, 2341
(a-1)(b-2)(c-3)(d+2019)=2020
a = 2
b =3
c =4
d =1
(2 - 1)(3 - 2)(4 - 3)(1 + 2019) = 2020
1*1*1*2020 = 2020
b = 1
c = 2
d = 1
(2 - 1)(1 - 2)(2 - 3)(1 + 2019) = 2020
1*(-1)*(-1)*2020 = 2020
