n,m,a,b=map(int,input().split())

mod=998244353
framod=[1]
def framod_calc(n, mod, a=1):
    for i in range(1,n+1):
        a=a * i % mod
        framod.append(a)
framod_calc(m, mod)

def permmod(n, k, mod):
    if n<k: return 0
    a=framod[n]
    c=framod[n-k]
    return (a * pow(c, mod-2, mod)) % mod

def combmod(n, k, mod):
    if n<k: return 0
    a=framod[n]
    b=framod[k]
    c=framod[n-k]
    return (a * pow(b, mod-2, mod) * pow(c, mod-2, mod)) % mod

tmp=0
for res in range(b-(n-1)*a+1):
    tmp+=combmod(n+res-2,res,mod)*(m-res-a*(n-1))
    tmp%=mod

print(tmp*permmod(n,n,mod)%mod)