N,K = map(int,input().split())
MOD = 10**9+7
A = list(range(N+1))
A[0] = 1
for i in range(1,N+1):
    A[i] = A[i-1]*i%MOD
B = list(range(N+1))
B[0] = 1
B[N] = pow(A[N],MOD-2,MOD)
for i in range(N-1,0,-1):
    B[i] = B[i+1]*(i+1)%MOD
def perm(n,k):
    if k>n:return 0
    return A[n]*B[n-k]%MOD
ans = ((perm(N-1,K)+K*(K-1)//2*perm(N-2,K-2))*N*(N-1)//2+N*perm(N-1,K))%MOD
print(ans)