N, M, A, B = map(int, input().split())
if B<(N-1)*A:
    exit(print(0))
fac = [0]*(N+M+1)
inv = [0]*(N+M+1)
fac[0]=inv[0]=1
mod = 998244353
for i in range(1,N+M+1):
    fac[i] = (fac[i-1]*i)%mod
    inv[i] = (inv[i-1]*pow(i,mod-2,mod))%mod

res = 0
for i in range(B-(N-1)*A+1):
    res += ((M-i-(N-1)*A)*fac[i+N-2]*inv[i]*inv[N-2]*fac[N])%mod
    res %= mod
print(res)