import sys
input = sys.stdin.readline
from collections import deque

N,M,A,B=map(int,input().split())
mod=998244353

FACT=[1]
for i in range(1,3*10**5+1):
    FACT.append(FACT[-1]*i%mod)

FACT_INV=[pow(FACT[-1],mod-2,mod)]
for i in range(3*10**5,0,-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]*FACT_INV[a-b]%mod
    else:
        return 0

ANS=0
for start in range(1,M+1):
    kosuu=min(M,start+B)-start
    #print(kosuu)
    if kosuu < 0:
        break
    

    ANS+=Combi(kosuu-(N-1)*(A-1),N-1)
    #print(ANS*FACT[N]%mod)

print(ANS*FACT[N]%mod)