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

h,w,a,b = map(int,input().split())
mod = 998244353
mn =  a
for i in range(a+1)[::-1]:
    if h-2*a+i >= 0:
        mn = i

six = pow(6, mod-2, mod)
two = pow(2, mod-2, mod)
def calc(x):
    tmp = x*(x+1)*(2*x+1)*six%mod + (h-2*a+1)*x*(x+1)*two%mod
    tmp%= mod
    return tmp
all = 0
for i in range(b+1):
    if w-2*b+i < 0: continue
    c = (w-(2*b-i)+1)*i
    tmp = c*(calc(a))
    if mn >= 1:
        tmp -= c*(calc(mn-1))
        tmp %= mod
    if i == b:
        tmp *= 2
        tmp -= i*a*(h-a+1)*(w-2*b+i+1)
    else:
        tmp *= 4
        tmp -= 2*i*a*(h-a+1)*(w-2*b+i+1)
    all += tmp
    all %= mod

tot = (a*b*2)*(h-a+1)*(w-b+1)*(h-a+1)*(w-b+1)
ans = (tot-all)*pow((h-a+1)*(w-b+1)*(h-a+1)*(w-b+1), mod-2, mod) % mod
ans %= mod
print(ans)