[tzc3012:Fibnacci Numbers]降幂公式+矩阵快速幂+斐波那契求和公式

题目链接：http://acm.tzc.edu.cn/acmhome/problemdetail.do?&method=showdetail&id=3012

Description

The fibnacci numbers are as follows:
f[1] = 1; f[2] = 2;
f[n] = f[n - 1] + f[n - 2];
And s[n] is defined:

Now ,give you the integer number a, x and n, you should calculate the ans, and the ans is defined as follows:
ans = a^s[x] % n;