C++ :

#include <bits/stdc++.h>
using namespace std;

int main() {
	int m, n, res;
	while (cin >> m >> n) {
		if (m == 0 && n == 0) return 0;
		
		res = 1;
		for (; n; n >>= 1) {
			if (n & 1) res = res * m % 10000;
			m = m * m % 10000;
		}
		printf("%04d\n", res);
	}	

	return 0;
}

Java :

import java.math.BigInteger;
import java.util.Scanner;

public class Main{
	public static void main(String[] args) {
		Scanner cin=new Scanner(System.in);
		while (cin.hasNext()) {
			 int m =cin.nextInt();
			 int n =cin.nextInt();
			 BigInteger b=new BigInteger(m+"");
			if (m!=0&&n!=0) {
				String ans=b.pow(n).toString();
				System.out.println(ans.length()>=4?ans.substring(ans.length()-4):
					String.valueOf((int)Math.pow(10, 4-ans.length())).substring(1)+ans);
			}
		}
	}
}