为啥打了快速幂还不过啊

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
ll qp(ll a,ll b){
	ll ans=1;
	while(b>0){
		if(b&1) ans*=a;
		a*=a;
		b>>=1;
	}
	return ans;
}
int main(){
	ll a,b;
	cin>>a>>b;
	if(a==1){
		cout<<1;
		return 0;
	}
	if(qp(a,b)<=1000000000) cout<<qp(a,b);
	else cout<<"-1";
        return 0;
}