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

n = 505050
mod = 998244353

fact = [1] * (n + 1)
inv = [1] * (n + 1)
for i in range(1, n):
    fact[i + 1] = ((i+1) * fact[i]) % mod
inv[n] = pow(fact[n], mod - 2, mod)
for i in range(n - 1, -1, -1):
    inv[i] = inv[i + 1] * (i + 1) % mod

def comb(n, r):
    if n < 0 or r < 0 or n - r < 0:
        return 0
    return fact[n] * inv[r] * inv[n - r] % mod

ans = 0
for x in range(B - A * (N - 1) + 1):
    ans += comb(x + N - 2, x) * (M - A * (N - 1) - x)
ans *= fact[N]
ans %= mod

print(ans)