# AB2個面積からダブり部分面積を引く、ダブり面積は1次元ずつ数えてその積
# 1次元W, Bを考えたとき、置き方総数は(W+1-B)の2乗
# 1個ダブるのはWに(2B-1)を置く数だからW+1-(2B-1)、左右入れ替え可能で2倍
# 2個ダブるのはWに(2B-2)を置く数だからW+1-(2B-2)、左右入れ替え可能で2倍

H, W, A, B = map(int, input().split())

from collections import defaultdict

# 横
yoko_dic = defaultdict(int)
for j in range(1, B+1):
    if j == B:
        yoko_dic[j] = W+1-(2*B-j)
    else:
        yoko_dic[j] = (W+1-(2*B-j))*2
yoko_total = (W+1-B)**2
yoko_dic[0] = yoko_total-sum(yoko_dic.values())
        
# 縦
tate_dic = defaultdict(int)
for i in range(1, A+1):
    if i == A:
        tate_dic[i] = H+1-(2*A-i)
    else:
        tate_dic[i] = (H+1-(2*A-i))*2
tate_total = (H+1-A)**2
tate_dic[0] = tate_total-sum(tate_dic.values())
        
'''
# 確率バージョン
ans = 0
for y in yoko_dic:
    for t in tate_dic:
        yoko_prob = yoko_dic[y]/yoko_total
        tate_prob = tate_dic[t]/tate_total
        area = A*B*2-y*t
        calc = area*yoko_prob*tate_prob
        ans += calc
print(ans)
'''

# modバージョン
mod = 998244353
ans = 0
yoko_total_inv = pow(yoko_total, mod-2, mod)
tate_total_inv = pow(tate_total, mod-2, mod)

for y in yoko_dic:
    for t in tate_dic:
        yoko_prob = yoko_dic[y]*yoko_total_inv
        tate_prob = tate_dic[t]*tate_total_inv
        area = A*B*2-y*t
        calc = (area*yoko_prob*tate_prob)%mod
        ans += calc
        ans %= mod
print(ans)