各位有什么好的思路吗？逆向思维好考虑

逆向思维好考虑，就是用总的情况数，减去不可能出现坏账的情况。但是用的BigInteger超时了

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

public class laoxu {
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        BigInteger w = in.nextBigInteger();
        BigInteger temp = pow2(w,n);
        BigInteger x = BigInteger.valueOf(1);
        BigInteger n_temp = BigInteger.valueOf(n);
        BigInteger w_cha = w.subtract(x);
        BigInteger y = pow2(w_cha,n-1).multiply(n_temp);
        BigInteger res = temp.subtract(y);
        BigInteger tt = BigInteger.valueOf(100003);
        System.out.println(res.remainder(tt));
    }

    public static BigInteger pow2(BigInteger x, int n) {
        if (n == 0)
            return BigInteger.valueOf(1);
        else {
            if (n % 2 == 0)
                return pow2(x.multiply(x), n / 2);
            else
                return pow2(x.multiply(x), (n - 1) / 2).multiply(x);
        }
    }
}