MOD = 10 ** 9 + 7
N, M = map(int, input().split())
dp = [[0] * (N - M + 1) for _ in range(M + 1)]
dp[1][0] = M
for i in range(M + 1):
    for j in range(N - M + 1):
        if i > 0:
            dp[i][j] += dp[i - 1][j] * (M - i + 1)
        if j > 0:
            dp[i][j] += dp[i][j - 1] * i
        dp[i][j] %= MOD
print(dp[M][N - M])