MOD = 998244353

h, w, a, b = map(int, input().split())


def f(n, k):
    ret = n * (n + 1) // 2 * k
    ret += n * (n + 1) * (2 * n + 1) // 6
    return ret % MOD


row = 2 * (f(a - 1, h - 2 * a + 1) - f(max(1, 2 * a - h) - 1, h - 2 * a + 1))
row += a * (h - a + 1)

col = 2 * (f(b - 1, w - 2 * b + 1) - f(max(1, 2 * b - w) - 1, w - 2 * b + 1))
col += b * (w - b + 1)

ans = row * col % MOD
ans *= pow((h - a + 1) ** 2 * (w - b + 1) ** 2, -1, MOD)
ans = 2 * a * b - ans
print(ans % MOD)