import sys
input = sys.stdin.readline

X,Y,Z,W=map(int,input().split())

mod=998244353

FACT=[1]
for i in range(1,2*10**6+1):
    FACT.append(FACT[-1]*i%mod)

FACT_INV=[pow(FACT[-1],mod-2,mod)]
for i in range(2*10**6,0,-1):
    FACT_INV.append(FACT_INV[-1]*i%mod)

FACT_INV.reverse()

def Combi(a,b):
    if 0<=b<=a:
        return FACT[a]*FACT_INV[b]%mod*FACT_INV[a-b]%mod
    else:
        return 0


if Z==0:
    X,Y=Y,X
    Z,W=W,Z

A=X-Z
B=Y-W

ANS=Y*Combi(X,A)*Combi(Y-1,B-1)*FACT[A+B-1]%mod

print(ANS)