class Combination:
    def __init__(self, size, mod=10**9 + 7):
        self.size = size + 2
        self.mod = mod
        self.fact = [1, 1] + [0] * size
        self.factInv = [1, 1] + [0] * size
        self.inv = [0, 1] + [0] * size

        for i in range(2, self.size):
            self.fact[i] = self.fact[i - 1] * i % self.mod
            self.inv[i] = -self.inv[self.mod % i] * (self.mod // i) % self.mod
            self.factInv[i] = self.factInv[i - 1] * self.inv[i] % self.mod

    def npr(self, n, r):
        if n < r or n < 0 or r < 0:
            return 0
        return self.fact[n] * self.factInv[n - r] % self.mod

    def ncr(self, n, r):
        if n < r or n < 0 or r < 0:
            return 0
        return self.fact[n] * (self.factInv[r] * self.factInv[n - r] % self.mod) % self.mod

    def factN(self, n):
        if n < 0:
            return 0
        return self.fact[n]

N, K = map(int, input().split())
MOD = 10**9 + 7
comb = Combination(N + 10)
ans = comb.npr(N - 1, K) * (N * (N + 1) // 2) + (N * (N - 1)) * comb.ncr(N - 2, K - 2) * comb.factN(K) // 4

print(ans % MOD)