import sys def input(): return sys.stdin.readline().strip() def list2d(a, b, c): return [[c] * b for i in range(a)] def list3d(a, b, c, d): return [[[d] * c for j in range(b)] for i in range(a)] def list4d(a, b, c, d, e): return [[[[e] * d for j in range(c)] for j in range(b)] for i in range(a)] def ceil(x, y=1): return int(-(-x // y)) def INT(): return int(input()) def MAP(): return map(int, input().split()) def LIST(N=None): return list(MAP()) if N is None else [INT() for i in range(N)] def Yes(): print('Yes') def No(): print('No') def YES(): print('YES') def NO(): print('NO') sys.setrecursionlimit(10 ** 9) INF = 10 ** 19 MOD = 10 ** 9 + 7 EPS = 10 ** -10 class ModTools: """ 階乗・逆元用のテーブルを構築する """ def __init__(self, MAX, MOD): # nCrならn、nHrならn+rまで作る MAX += 1 self.MAX = MAX self.MOD = MOD factorial = [1] * MAX factorial[0] = factorial[1] = 1 for i in range(2, MAX): factorial[i] = factorial[i-1] * i % MOD inverse = [1] * MAX inverse[MAX-1] = pow(factorial[MAX-1], MOD-2, MOD) for i in range(MAX-2, -1, -1): inverse[i] = inverse[i+1] * (i+1) % MOD self.fact = factorial self.inv = inverse def nCr(self, n, r): """ 組み合わせ """ if n < r: return 0 r = min(r, n-r) numerator = self.fact[n] denominator = self.inv[r] * self.inv[n-r] % self.MOD return numerator * denominator % self.MOD def nHr(self, n, r): """ 重複組み合わせ """ return self.nCr(r+n-1, r) def nPr(self, n, r): """ 順列 """ if n < r: return 0 return self.fact[n] * self.inv[n-r] % self.MOD N, K = MAP() mt = ModTools(N, MOD) cnt = mt.nPr(N-1, K) + mt.nCr(K, 2)*mt.nPr(N-2, K-2) % MOD ans = 0 for i in range(N): ans += i * cnt ans %= MOD ans += N * mt.nPr(N-1, K) ans %= MOD print(ans)