#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <iomanip>
#include <cmath>
#include <stdio.h>
#include <queue>
#include <deque>
#include <cstdio>
#include <set>
#include <map>
#include <bitset>
#include <stack>
#include <cctype>
using namespace std;
long long mod = 1000000007;
long long m_pow(long long x, long long y) {
	long long ans = 1;
	while (y > 0) {
		if ((y & 1) == 1) {
			ans = ans * x % mod;
		}
		x = x * x % mod;
		y >>= 1;
	}
	return ans;
}
int main() {
	long long n, k;
	cin >> n >> k;
	cout << (m_pow(n, k + 1) - (n * m_pow(n - 1, k) % mod) + mod) % mod << endl;
	
}