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); //--------------------------------- }