using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var c = NList;
        var (h, w, a, b) = (c[0], c[1], c[2], c[3]);
        WriteLine(Sheets(h, w, a, b));
    }
    static long Sheets(int h, int w, int a, int b)
    {
        var mod = 998_244_353;
        var p = 0L;
        var q = 0L;
        for (var i = 1; i <= a; ++i)
        {
            var count = h + i - 2L * a + 1;
            if (count < 0) continue;
            if (i < a) count *= 2;
            p = (p + count % mod * i % mod) % mod;
        }
        for (var j = 1; j <= b; ++j)
        {
            var count = w + j - 2L * b + 1;
            if (count < 0) continue;
            if (j < b) count *= 2;
            q = (q + count % mod * j % mod) % mod;
        }
        var hp = Exp(h - a + 1, mod - 2, mod);
        var wp = Exp(w - b + 1, mod - 2, mod);
        return (2L * a * b - p * q % mod * hp % mod * hp % mod * wp % mod * wp % mod + mod) % mod;
    }
    static long Exp(long n, long p, int mod)
    {
        long _n = n % mod;
        var _p = p;
        var result = 1L;
        if ((_p & 1) == 1) result *= _n;
        while (_p > 0)
        {
            _n = _n * _n % mod;
            _p >>= 1;
            if ((_p & 1) == 1) result = result * _n % mod;
        }
        return result;
    }
}