N, K = map(int, input().split())
power = [1 for i in range(10**5+10)]
mod = 10**9+7
for i in range(1, 10**5+10):
    power[i] = power[i-1]*i % mod


def rev(X):
    return pow(X, mod-2, mod)


def P(n, k):
    if n < k:
        return 0
    if n < 0 or k < 0:
        return 0
    else:
        return power[n]*rev(power[n-k]) % mod


ans = N*(N-1)//2
ans *= (P(N-1, K)+K*(K-1)//2*P(N-2, K-2))
ans %= mod
ans += N*P(N-1, K)
ans %= mod
print(ans)