n, m = map(int, input().split())
mod = 10**9+7


P = [1]*(m+1)
Q = [1]*(m+1)
inv = [1]*(m+1)
for i in range(2, m+1):
  P[i] = P[i-1]*i%mod
  a, b = divmod(mod, i)
  # print(a, b, inv[b], i)
  inv[i] = (-a*inv[b])%mod
  Q[i] = Q[i-1]*inv[i]%mod

comb = lambda x, y: P[x]*Q[y]*Q[x-y]%mod if 0<=y<=x else 0

t = 1
ans = 0
for i in range(m+1)[::-1]:
  ans += comb(m, i)*pow(i, n, mod)*t
  t = -t
  ans %= mod

print(ans)