/* -*- coding: utf-8 -*-
 *
 * 823.cc:  No.823 Many Shifts Easy - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 100000;
const int MOD = 1000000007;

/* typedef */

typedef long long ll;

/* global variables */

ll fracs[MAX_N + 1];

/* subroutines */

inline ll powmod(ll a, int n) {  // a^n % MOD
  ll pm = 1;
  while (n > 0) {
    if (n & 1) pm = (pm * a) % MOD;
    a = (a * a) % MOD;
    n >>= 1;
  }
  return pm;
}

inline ll inv(ll a) { return powmod(a, MOD - 2); }

inline ll npk(int n, int k) {
  if (n < 0 || k < 0 || n < k) return 0;
  return fracs[n] * inv(fracs[n - k]) % MOD;
}

inline ll nck(int n, int k) {
  if (n < 0 || k < 0 || n < k) return 0;
  return npk(n, k) * inv(fracs[k]) % MOD;
}

/* main */

int main() {
  int n, k;
  scanf("%d%d", &n, &k);

  fracs[0] = 1;
  for (int i = 1; i <= n; i++) fracs[i] = fracs[i - 1] * i % MOD;

  ll inv2 = inv(2LL);

  ll a =
    (ll)n * (n + 1) % MOD * inv2 % MOD * npk(n - 1, k) % MOD;

  ll b =
    (ll)n * (n - 1) % MOD * inv2 % MOD * nck(n - 2, k - 2) % MOD *
    fracs[k] % MOD * inv2 % MOD;

  printf("%lld\n", (a + b) % MOD);
  return 0;
}