def cominit(n, mod):
  global fac, finv
  fac = [1] * n
  finv = [1] * n
  for i in range(2, n):
    fac[i] = (fac[i-1] * i) % mod
    finv[i] = (finv[i-1] * pow(i, mod-2, mod)) % mod

def comb(n, k):
  global mod
  if n < k:
    return 0
  if n < 0 or k < 0:
    return 0
  return (fac[n] * finv[n-k] % mod) * finv[k] % mod

mod = 998244353
cominit(400000, mod)

n, m, a, b = map(int, input().split())
ans = 0
for i in range(m):
  if a * (n - 1) + i > b:
    break
  ans += (m - (a * (n - 1) + i)) * fac[n] * comb(n-1+i-1, i)
  ans %= mod
print(ans)