from collections import defaultdict, deque, Counter
from heapq import heapify, heappop, heappush
import math
from copy import deepcopy
from itertools import combinations, permutations, product, combinations_with_replacement
from bisect import bisect_left, bisect_right

import sys

def input():
    return sys.stdin.readline().rstrip()
def getN():
    return int(input())
def getNM():
    return map(int, input().split())
def getList():
    return list(map(int, input().split()))
def getListGraph():
    return list(map(lambda x:int(x) - 1, input().split()))
def getArray(intn):
    return [int(input()) for i in range(intn)]

mod = 10 ** 9 + 7
MOD = 998244353
sys.setrecursionlimit(10000000)
inf = float('inf')
eps = 10 ** (-15)
dy = [0, 1, 0, -1]
dx = [1, 0, -1, 0]

#############
# Main Code #
#############

lim = 10 ** 6 + 1
fact = [1, 1]
factinv = [1, 1]
inv = [0, 1]

for i in range(2, lim + 1):
    fact.append((fact[-1] * i) % mod)
    inv.append((-inv[mod % i] * (mod // i)) % mod)
    # 累計
    factinv.append((factinv[-1] * inv[-1]) % mod)

def cmb(n, r):
    if (r < 0) or (n < r):
        return 0
    r = min(r, n - r)
    return fact[n] * factinv[r] * factinv[n - r] % mod

"""
条件
Ui: 色iを含まない　
U0 & U2 & U3: 色0と色2と色3を含まない
"""

N, M = getNM()
ans = 0
for i in range(M):
    ans += pow(M - i, N, mod) * cmb(M, i) * ((-1) ** (i % 2))
    ans %= mod
print(ans)