fn main() {
	let mut s = String::new();
	std::io::stdin().read_line(&mut s).ok();
	let n: Vec<u64> = s.split_whitespace().flat_map(str::parse).collect();
	let x = (0..).find(|x| x % n[0] == n[2] && x % n[1] == n[3]);
	println!("{}", x.unwrap());
}