/*
timing:
first submision 36m
bug fixing 10m
*/
#include <bits/stdc++.h>
using namespace std;
typedef long long int lint;
typedef long double ldouble;

const lint mod = 1e9 + 7;

vector<int> p;
int n, k;

void genNext(int x) {
	for (int i = k - 1; i >= 0; --i, x /= k)
		p[i] = x % k;
}

bool check() {
	for (int i = 0; i < k; ++i) {
		int c = p[i];
		int j = 0;
		while (c != 0 && j <= k) {
			c = p[c];
			++j;
		}
		if (c != 0)
			return false;
	}
	return true;
}

int powm(int x, int a) {
	if (a == 0)
		return 1;

	lint res = x;
	lint y = a;
	y /= 2;
	int i = 0;
	while (y) {
		res = (res * res)%mod;
		y /= 2;
		++i;
	}
	i = a - pow(2, i);
	while (i > 0) {
		res = (res * x)%mod;
		--i;
	}
	return res;
}

int main(int, char**) {
	cin >> n >> k;
	p.resize(k);

	lint count = 0LL;
	int ntuples = pow(k, k) - 1;
	for (int i = 0; i <= ntuples; ++i) {
		genNext(i);
		if (check()) {
			++count;
		}
	}

	cout << (count * powm(n-k,n-k))%mod << endl;

	return 0;
}