kaijou = [1]
kaijou_ = [1]
mod = 10**9 + 7
for i in range(1,10**5+1):
  k = kaijou[-1]*i
  k %= mod
  kaijou.append(k)
  k = pow(k,mod-2,mod)
  kaijou_.append(k)

def comb(n,r):
  res = kaijou_[n-r]*kaijou_[r]
  res %= mod
  res *= kaijou[n]
  res %= mod
  return res

N,M = map(int,input().split())
ans = 0
for k in range(M):
  res = comb(M,k)
  if k % 2 == 1:
    res *= -1
    res %= mod
  res *= pow(M-k,N,mod)
  res %= mod
  ans += res
  ans %= mod
print(ans)