ZOJ Problem Set - 1489
Give a number n, find the minimum x that satisfies 2^x mod n = 1.
One positive integer on each line, the value of n.
If the minimum x exists, print a line with 2^x mod n = 1.
Print 2^? mod n = 1 otherwise.
You should replace x and n with specific numbers.
2^? mod 2 = 1
Author: MA, Xiao
Source: ZOJ Monthly, February 2003