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)