#include <iostream>
using namespace std;

long long N, K, fact[200009], factinv[200009], mod = 1000000007;

long long modpow(long long a, long long b, long long m) {
	long long p = 1, q = a;
	for (int i = 0; i < 32; i++) {
		if ((b / (1LL << i)) % 2 == 1) { p *= q; p %= m; }
		q *= q; q %= m;
	}
	return p;
}

long long Div(long long a, long long b, long long m) {
	return (a * modpow(b, m - 2, m)) % m;
}

void init() {
	fact[0] = 1; for (int i = 1; i <= 200000; i++) fact[i] = (1LL * i * fact[i - 1]) % mod;
	for (int i = 0; i <= 200000; i++) factinv[i] = Div(1, fact[i], mod);
}

long long ncr(long long n, long long r) {
	if (n < r || r < 0) return 0;
	return (fact[n] * factinv[r] % mod) * factinv[n - r] % mod;
}

int main() {
	cin >> N >> K; init();
	long long B1 = ncr(N - 1, K) * fact[K] % mod;
	long long B2 = ncr(N - 2, K - 2) * fact[K] % mod; B2 *= factinv[2]; B2 %= mod;

	long long R = N * (N - 1) / 2; R %= mod;
	cout << ((B1 + B2) * R + B1 * N) % mod << endl;
	return 0;
}