MOD = 10 ** 9 + 7
N = 200000
fact = [0 for _ in range(N)]
invfact = [0 for _ in range(N)]
fact[0] = 1
for i in range(1, N):
    fact[i] = fact[i - 1] * i % MOD

invfact[N - 1] = pow(fact[N - 1], MOD - 2, MOD)

for i in range(N - 2, -1, -1):
    invfact[i] = invfact[i + 1] * (i + 1) % MOD

def nCk(n, k):
    if k < 0 or n < k:
        return 0
    else:
        return (fact[n] * invfact[k] % MOD) * invfact[n - k] % MOD

def nHk(n, k):
    return nCk(n + k - 1, k)
    
def nPk(n, k):
    if k < 0 or n < k:
        return 0
    else:
        return fact[n] * invfact[n - k] % MOD

n, k = map(int, input().split())
ans = nPk(n - 1, k)
ans += nCk(n - 2, k - 2) * fact[k] * invfact[2] % MOD
ans *= n * (n - 1) // 2
ans %= MOD
ans += nPk(n - 1, k) * n
print(ans % MOD)