import java.io.PrintWriter;
import java.util.Arrays;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		new Main().run();
	}

	long MOD = 1_000_000_000 + 7;
	long[] inv = new long[10002];
	long[] B = new long[10001];
	{
		inv[1] = 1;
		for (int i = 2; i < inv.length; ++i) {
			inv[i] = MOD - inv[(int) (MOD % i)] * (MOD / i) % MOD;
		}
		B[0] = 1;
		for (int i = 1; i < B.length; ++i) {
			long C = 1;
			for (int j = 0; j < i; ++j) {
				B[i] += (MOD - C * B[j] % MOD) % MOD;
				B[i] %= MOD;
				C = C * (i + 1 - j) % MOD * inv[j + 1] % MOD;
			}
			B[i] = B[i] * inv(i + 1) % MOD;
		}
	}

	public void run() {
		Scanner sc = new Scanner(System.in);
		long n = sc.nextLong();
		int k = sc.nextInt();
		long ans = 0;
		long C = 1;
		for (int i = 0; i <= k; ++i) {
			ans += C * B[i] % MOD * pow(n, k + 1 - i) % MOD * (i % 2 == 0 ? 1 : MOD - 1) % MOD;
			ans %= MOD;
			C = C * (k + 1 - i) % MOD * inv[i + 1] % MOD;
		}
		ans = ans * inv(k + 1) % MOD;
		System.out.println(ans);
	}

	long inv(long a) {
		return pow(a, MOD - 2);
	}

	long pow(long a, long n) {
		long ret = 1;
		a %= MOD;
		for (; n > 0; n >>= 1, a = a * a % MOD) {
			if (n % 2 == 1) {
				ret = ret * a % MOD;
			}
		}
		return ret;
	}

	static void tr(Object... objects) {
		System.out.println(Arrays.deepToString(objects));
	}
}