MOD = 10 ** 9 + 7

n, m = map(int, input().split())

fact = [1 for _ in range(n + 1)]
inv = [1 for _ in range(n + 1)]
ifact = [1 for _ in range(n + 1)]
for x in range(2, n + 1):
  fact[x] = (fact[x - 1] * x) % MOD
  inv[x] = (- (MOD // x) * inv[MOD % x]) % MOD
  ifact[x] = (ifact[x - 1] * inv[x]) % MOD

ans = 0
for i in range(m + 1):
  if (m - i) % 2 == 0:
    ans = (ans + fact[m] * ifact[m - i] * ifact[i] * pow(i, n, MOD)) % MOD
  else:
    ans = (ans - fact[m] * ifact[m - i] * ifact[i] * pow(i, n, MOD)) % MOD

print(ans)