import sys
sys.setrecursionlimit(5*10**5)
input = sys.stdin.readline
from collections import defaultdict, deque, Counter
from heapq import heappop, heappush
from bisect import bisect_left, bisect_right
from math import gcd

mod = 998244353
# nCk
def com(n, mod):
    fact = [1, 1]
    factinv = [1, 1]
    inv = [0, 1]
    for i in range(2, n+1):
        fact.append((fact[-1]*i) % mod)
        inv.append((-inv[mod % i]*(mod//i)) % mod)
        factinv.append((factinv[-1]*inv[-1]) % mod)
    return fact, factinv


f,fi = com(3*10**5+10, mod)

def npr(n, r,):
    return f[n] * fi[n-r] % mod
def ncr(n, r):
    return f[n] * fi[n-r] % mod * fi[r] % mod

x,y,z,w = map(int,input().split())

if w == 0:
    print(npr(x,x-z)*npr(y,y-w)%mod*ncr(x+y-(w+z)-1, x-z)%mod)
else:
    print(npr(x,x-z)*npr(y,y-w)%mod*ncr(x+y-(w+z)-1, y-w)%mod)