#include <bits/stdc++.h>
#include <atcoder/all>
using mint = atcoder::modint1000000007;
using namespace std;

int main() {
	int n, m;
	cin >> n >> m;
	mint ans = 1;
	for (int i = 0; i < m; i++){
		ans *= (n - i);
	}
	ans *= (mint(m)).pow(max(0, n - m - 1));
	cout << ans.val() << endl;
}