#############################################################

import sys
sys.setrecursionlimit(10**7)

from heapq import heappop,heappush
from collections import deque,defaultdict,Counter
from bisect import bisect_left, bisect_right
from itertools import product,combinations,permutations
from math import sin,cos
#from math import isqrt #DO NOT USE PyPy

ipt = sys.stdin.readline
iin = lambda :int(ipt())
lmin = lambda :list(map(int,ipt().split()))

MOD = 998244353
#############################################################

K = 10**6

factorial = [1, 1]
inverse = [1, 1]
invere_base = [0, 1]
for i in range(2, K + 1):
    factorial.append((factorial[-1] * i) % MOD)
    invere_base.append((-invere_base[MOD % i] * (MOD // i)) % MOD) #逆元
    inverse.append((inverse[-1] * invere_base[-1]) % MOD) #階乗逆元

#combination
def nCr(n, r):
    if (r < 0 or r > n):
        return 0
    r = min(r, n - r)
    return factorial[n] * inverse[r] % MOD * inverse[n - r] % MOD

def nPr(n,r):
    if (r < 0 or r > n):
        return 0
    return factorial[n] * inverse[n-r] % MOD


X,Y,Z,W = lmin()
if Z == 0:
    print(nCr(X+Y-W-1,X-1)*nPr(X,X)*nPr(Y,Y-W)%MOD)
else:
    print(nCr(X-Z+Y-1,Y-1)*nPr(Y,Y)*nPr(X,X-Z)%MOD)