def combs_mod(n,k,mod):
  #kCkからnCkまで
  inv = [1]*(n-k+1)
  for i in range(1,n-k+1):
    inv[i] = pow(i,mod-2,mod)
  ans = [1]*(n+1)
  for i in range(k+1,n+1):
    ans[i] = ans[i-1]*i*inv[i-k]%mod
  return ans
def solve():
  N, M, A, B = map(int, input().split())
  mod = 998244353
  p = B-(N-1)*A
  if p<0:
    return 0
  lis = combs_mod(p+N-1,N-1,mod)
  ans = lis[p+N-1]*(M-B)%mod
  for i in range(p):
    ans += lis[i+N-1]
    ans %= mod
  for i in range(2,N+1):
    ans *= i
    ans %= mod
  return ans
print(solve())