Description has only two Sentences 程序实现

Problem Description
an = X*an-1 + Y and Y mod (X-1) = 0.
Your task is to calculate the smallest positive integer k that ak mod a0 = 0.

Input
Each line will contain only three integers X, Y, a0 ( 1 < X < 231, 0 <= Y < 263, 0 < a0 < 231).

Output
For each case, output the answer in one line, if there is no such k, output "Impossible!".

Sample Input
2 0 9

Sample Output
1