import sys
import pypyjit
import itertools
import heapq
import math
from collections import deque, defaultdict
import bisect

input = sys.stdin.readline
sys.setrecursionlimit(10 ** 6)
pypyjit.set_param('max_unroll_recursion=-1')


def index_lt(a, x):
    'return largest index s.t. A[i] < x or -1 if it does not exist'
    return bisect.bisect_left(a, x) - 1


def index_le(a, x):
    'return largest index s.t. A[i] <= x or -1 if it does not exist'
    return bisect.bisect_right(a, x) - 1


def index_gt(a, x):
    'return smallest index s.t. A[i] > x or len(a) if it does not exist'
    return bisect.bisect_right(a, x)


def index_ge(a, x):
    'return smallest index s.t. A[i] >= x or len(a) if it does not exist'
    return bisect.bisect_left(a, x)


class Combination:
    def __init__(self, N, p):
        self.N = N
        self.p = p
        self.f = [None] * (N + 1)
        self.finv = [None] * (N + 1)
        self.inv = [None] * (N + 1)

        self.f[0] = 1
        self.f[1] = 1
        self.finv[0] = 1
        self.finv[1] = 1
        self.inv[1] = 1
        for i in range(2, N + 1):
            self.f[i] = self.f[i - 1] * i % p
            self.inv[i] = p - self.inv[p % i] * (p // i) % p
            self.finv[i] = self.finv[i - 1] * self.inv[i] % p

    def P(self, n, k):
        if n < k:
            return 0
        if n < 0 or k < 0:
            return 0
        return self.f[n] * self.finv[n - k] % self.p

    def C(self, n, k):
        if n < k:
            return 0
        if n < 0 or k < 0:
            return 0
        return self.f[n] * (self.finv[k] * self.finv[n - k] % self.p) % self.p

    # 重複組合せ
    # n種類のものからk個選ぶ
    def H(self, n, k):
        return self.C(k + n - 1, k)


N, M = map(int, input().split())
mod = 10 ** 9 + 7

comb = Combination(N, mod)
acc = 0
for i in range(M):
    if i & 1:
        acc -= comb.C(M, i) * pow(i, N, mod) % mod
    else:
        acc += comb.C(M, i) * pow(i, N, mod) % mod
    acc %= mod
print((pow(M, N, mod) - acc) % mod)