import java.util.Arrays;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		solver();
	}

	static final long MOD = 1_000_000_007;

	static void solver() {
		Scanner sc = new Scanner(System.in);
		long n = sc.nextLong();
		int m = sc.nextInt();
		long[] mCk = nth_Pascal_triangle(m);
		long ans = 0;
		ans += pow(m, n);
		for (int i = 1; i <= m - 1; i++) {
			ans = ans + mCk[i] * pow(m - i, n) % MOD * (i % 2 == 0 ? 1 : -1);
			if (ans < 0)
				ans += MOD;
			ans%=MOD;
		}
		System.out.println(ans);

	}

	static long[] nth_Pascal_triangle(int n) {
		long[] ans = new long[n + 1];
		for (int i = 0; i <= n; i++) {
			long[] dp = Arrays.copyOf(ans, ans.length);
			for (int j = 0; j < i + 1; j++) {
				if (j == 0)
					ans[j] = 1;
				else if (j == i)
					ans[j] = 1;
				else {
					ans[j] = (dp[j - 1] + dp[j]) % MOD;
				}
			}
		}
		return ans;
	}

	static long pow(long a, long n) {
		long A = a;
		long ans = 1;
		while (n >= 1) {
			if (n % 2 == 0) {
				A = (A * A) % MOD;
				n /= 2;
			} else if (n % 2 == 1) {
				ans = ans * A % MOD;
				n--;
			}
		}
		return ans;
	}
}