N,K = map(int,input().split())
mod = 10 ** 9 + 7

C = N + 5
fact = [1] * C
for i in range(2,C):
    fact[i] = fact[i-1] * i % mod
fact_inv = [1] * C
fact_inv[-1] = pow(fact[-1],mod- 2,mod)
for i in range(C - 2,0,-1):
    fact_inv[i] = fact_inv[i + 1] * (i + 1) % mod
def c(n,k):
    if k > n or n < 0 or k < 0:
        return 0
    return fact[n] * fact_inv[k] % mod * fact_inv[n - k] % mod
def p(n,k):
    if k > n or k < 0 or n < 0:
        return 0
    return fact[n] * fact_inv[n - k] % mod
ans = 0
tmp = N * (N + 1) // 2 * p(N -1,K) % mod
ans += tmp
tmp = (N - 1) * N // 2 * c(K,2) % mod * p(N - 2,K - 2) % mod
ans += tmp
print(ans % mod)