用快速幂求乘积同时取模即可
#include<iostream>
using namespace std;
const long long MOD = 1000;
long long quick(long long a,long long b)
{
long long ans = 1;
while(b)
{
if(b&1) ans = ans*a%MOD;
b >>= 1;
a = a*a%MOD;
}
return ans;
}
int main()
{
long long a,b;
while(cin>>a>>b)
{
if(!a&&!b) break;
cout<<quick(a,b)<<endl;
}
}