#include <bits/stdc++.h>

using namespace std;

using ll = long long;

const ll MOD = 1000000007;

ll modpow(ll x, ll n, ll mod = MOD) {
    ll res = 1;
    while (n > 0) {
        if (n & 1) res = res * x % mod;
        x = x * x % mod;
        n >>= 1;
    }
    return res;
}

ll calc(int n, int k) {
    ll res = (n >= 0 && k >= 0);
    for (int i = 0; i < k; i++) {
        if (n - i < 0) break;
        (res *= (n - i)) %= MOD;
    }
    return res;
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    ll n, K;
    cin >> n >> K;
    
    ll div2 = (MOD + 1) / 2;

    ll foo = calc(n - 1, K);
    ll bar = calc(n - 2, K - 2);

    ll ans = (foo * n % MOD + (foo + K * (K - 1) % MOD * div2 % MOD * bar % MOD) % MOD * n % MOD * (n - 1) % MOD * div2 % MOD) % MOD;
    cout << ans << endl;
    return 0;
}