九度OJ 二分求幂法、快速取模之《root(n,k)》

//九度OJ 快速取模之《root(n,k)》
//http://ac.jobdu.com/problem.php?pid=1085
#include<stdio.h>
int k;
long fang(long a,long b)
{
long long ret=1;
while(b)
{
if(b&1)ret=ret*a%(k-1);
a=a*a%(k-1);
b>>=1;
}
return ret;
}
int main()
{
long long x,y;
int i;
while(~scanf("%lld %lld %d",&x,&y,&k))
{
long ret=fang(x,y);
if(!ret)ret=k-1;
printf("%lld\n",ret);
}
return 0;
}