void Solve(StreamScanner ss, StreamWriter sw)
{
//---------------------------------
var comb = new Combination(200010);
var H = ss.Next(int.Parse);
var W = ss.Next(int.Parse);
var A = ss.Next(int.Parse);
var B = ss.Next(int.Parse);
var ans = new ModInt(0);
for (var i = 0; i < H - A; i++)
{
ans += comb.NCK(B - 1 + i, B - 1) * comb.NCK(W - B - 1 + H - i - 1, W - B - 1);
}
sw.WriteLine(ans);
//---------------------------------
}
