local mod = 998244353
local mfl = math.floor
local function bmul(x, y)
  local x0, y0 = x % 31596, y % 31596
  local x1, y1 = mfl(x / 31596), mfl(y / 31596)
  return (x1 * y1 * 62863 + (x1 * y0 + x0 * y1) * 31596 + x0 * y0) % mod
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)
  local ret = 1
  local inv = 1
  for i = 1, k do
    ret = bmul(ret, n + 1 - i)
    inv = bmul(inv, i)
  end
  return bmul(ret, modinv(inv))
end

local x, y = io.read("*n", "*n")
local z, w = io.read("*n", "*n")
if z == 0 then
  x, y = y, x
  z, w = w, z
end
local fact = 1
for i = 2, x - z + y - 1 do
  fact = (fact * i) % mod
end
local ans = (fact * y) % mod
local c = getComb(x, z)
ans = bmul(ans, c)
print(ans)