fn main() {
	let mut s = String::new();
	std::io::stdin().read_line(&mut s).ok();
	let n: Vec<i64> = s.split_whitespace().flat_map(str::parse).collect();
	println!(
		"{}",
		n[0].min(n[1])
			+ match n[0] - n[1] {
				0 => 0,
				d if d > 0 => d / (n[2] + 1),
				d => -d / (n[3] + 1),
			},
	)
}