题目是快速幂取模

#include<bits/stdc++.h>
#define ll long long
using namespace std;
ll b,k,p;
ll a1(ll x){
	ll mid=x>>1;
	if(x==0)
		return 1;
	if(x==1)
		return b%p;
	if(x==2)
		return b%p*b%p;
	return a1(mid)*a1(x-mid)%p;
}
int main(){
	scanf("%lld%lld%lld",&b,&k,&p);
	printf("%lld",a1(k));
	return 0;
}

超时一个点qwq