# coding:UTF-8
import sys

MOD = 10 ** 9 + 7
INF = float('inf')

def combInit(n):
    fact = [1, 1]
    finv = [1, 1]
    inv = [0, 1]
    for i in range(2, n + 1):
        fact.append(fact[i - 1] * i % MOD)
        inv.append(MOD - inv[MOD % i] * (MOD // i) % MOD)
        finv.append(finv[i - 1] * inv[i] % MOD)
    return [fact, finv]

def comb(n, k, f):
    if n < k:
        return 0
    elif n < 0 or k < 0:
        return 0
    else:
        return f[0][n] * (f[1][k] * f[1][n - k] % MOD) % MOD

N, M = list(map(int, input().split()))     # スペース区切り連続数字

f = combInit(M)

res = 0
for i in range(M):
    if i % 2 == 0:
        res = (res + comb(M, i, f) * pow(M-i, N, MOD)) % MOD
    else:
        res = (res - comb(M, i, f) * pow(M-i, N, MOD)) % MOD

print("{}".format(res))