from collections import *
from itertools import *
from functools import *
from heapq import *
import sys,math
input = sys.stdin.readline
class combination():
    
    def __init__(self,N,p):
        
        
        self.fact = [1, 1]  # fact[n] = (n! mod p)
        self.factinv = [1, 1]  # factinv[n] = ((n!)^(-1) mod p)
        self.inv = [0, 1]  # factinv 計算用
        self.p = p
        
        for i in range(2, N + 1):
            self.fact.append((self.fact[-1] * i) % p)
            self.inv.append((-self.inv[p % i] * (p // i)) % p)
            self.factinv.append((self.factinv[-1] * self.inv[-1]) % p)
        

    def cmb(self,n, r):
        if (r < 0) or (n < r):
            return 0
        r = min(r, n - r)
        return self.fact[n] * self.factinv[r] * self.factinv[n-r] % self.p
        
        
X,Y,Z,W = map(int,input().split())
mod = 998244353
C = combination(X+Y,mod)
if W==0:
    X,Y = Y,X
    W,Z = Z,W

dx = X-1
dy = Y-W
print(C.cmb(dx+dy,dx)*C.fact[dy]*C.fact[dx+1]*C.cmb(X,dx+1)*C.cmb(Y,dy)%mod)