#!/usr/bin/env python3
# from typing import *

import sys
import io
import math
import collections
import decimal
import itertools
import bisect
import heapq


def input():
    return sys.stdin.readline()[:-1]


# sys.setrecursionlimit(1000000)

# _INPUT = """# paste here...
# """
# sys.stdin = io.StringIO(_INPUT)

MOD = 1000000007


def comb(n, r):
    r = min(r, n - r)
    return (fact[n] * factinv[r] * factinv[n-r]) % MOD

        
fact = [1, 1]  # fact[n] = (n! mod p)
factinv = [1, 1]  # factinv[n] = ((n!)^(-1) mod p)
inv = [0, 1]  # factinv 計算用

N, M = map(int, input().split())
for i in range(2, M + 1):
    fact.append((fact[-1] * i) % MOD)
    inv.append((-inv[MOD % i] * (MOD // i)) % MOD)
    factinv.append((factinv[-1] * inv[-1]) % MOD)

ans = 0
for k in range(M):
    ans += (-1)**k * comb(M, k) * pow(M-k, N, MOD)
ans %= MOD
print(ans)