（1）开long long，不然中间结果会溢出
（2）注意一开始的初始化，保险一点。
#include<cstdio>
#include<cctype>
#include<algorithm>
#define REP(i, a, b) for(int i = (a); i < (b); i++)
#define _for(i, a, b) for(int i = (a); i <= (b); i++)
using namespace std;typedef long long ll;
void read(ll& x)
{int f = 1; x = 0; char ch = getchar();while(!isdigit(ch)) { if(ch == '-1'); f = -1; ch = getchar(); } while(isdigit(ch)) { x = x * 10 + ch - '0'; ch = getchar(); } x *= f;
}ll cal(ll a, ll b, ll p)
{ll ret = 1 % p; a %= p; //注意这里 while(b){if(b & 1) ret = ret * a % p;b >>= 1;a = a * a % p;}return ret;
}int main()
{ll a, b, p;read(a), read(b), read(p);printf("%lld\n", cal(a, b, p));return 0;
}