2^x mod n = 1

Give a number n, find the minimum x(x>0) 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
5

2^? mod 2 = 1
2^4 mod 5 = 1

MA, Xiao

ZOJ Monthly, February 2003