三个tle，蒟蒻求助

#include<bits/stdc++.h>
using namespace std;
long long a,b,p;
int byd(long long j,long long k){
	if(k==0)return 1;
	if(k&1){
		return j*byd(j,k-1)%p;
	}if(!(k&1)){
		return byd(j,k/2)*byd(j,k/2)%p;
	}
}
int main(){
	cin>>a>>b>>p;
	cout<<a<<'^'<<b<<" mod "<<p<<'='<<byd(a,b);
	return 0;
}