local mod = 1000000007
local mfl = math.floor
local function badd(x, y) return (x + y) % mod end
local function bmul(x, y)
  local x1, y1 = mfl(x / 31623), mfl(y / 31623)
  local x0, y0 = x - x1 * 31623, y - y1 * 31623
  return (x1 * y1 * 14122 + (x1 * y0 + x0 * y1) * 31623 + x0 * y0) % mod
end

local n, m = io.read("*n", "*n")

local fact = {1}
local invs = {1}
local invfact = {1}
for i = 2, n do
  fact[i] = bmul(fact[i - 1], i)
  invs[i] = bmul(mfl(mod / i), mod - invs[mod % i])
  invfact[i] = bmul(invfact[i - 1], invs[i])
end

local function modpow(src, pow)
  local res = 1
  while 0 < pow do
    if pow % 2 == 1 then
      res = bmul(res, src)
      pow = pow - 1
    end
    src = bmul(src, src)
    pow = mfl(pow / 2)
  end
  return res
end

local function modinv(src)
  return modpow(src, mod - 2)
end

local function getComb(n, k)
  if k == 0 or n == k then return 1 end
  return bmul(fact[n], bmul(invfact[k], invfact[n - k]))
end
local ret = 0
for i = 1, m do
  local v = getComb(m, i)
  if 0 < i then
    v = bmul(v, modpow(i, n))
  end
  if (m - i) % 2 == 1 then
    v = (mod - v) % mod
  end
  ret = badd(ret, v)
end
print(ret)