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

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

ipt = sys.stdin.readline

def iin():
    return int(ipt())
def lmin():
    return list(map(int,ipt().split()))

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



H,W,A,B = lmin()
ans = A*B*2*((H-A+1)*(W-B+1))**2%MOD

SB = 0
SA = 0
for i in range(1,B):
    if 2*B-i > W:
        break
    SB += i*(W-B-(B-i)+1)
    SB %= MOD
for i in range(1,A):
    if 2*A-i > H:
        break
    SA += i*(H-A-(A-i)+1)
    SA %= MOD

ans -= 4*SA*SB%MOD
ans -= 2*A*(H-A+1)*SB%MOD
ans -= 2*B*(W-B+1)*SA%MOD
ans -= A*B*(H-A+1)*(W-B+1)%MOD
ans %= MOD

d = pow(((H-A+1)*(W-B+1))**2,MOD-2,MOD)
print(ans*d%MOD)