use std::io::Read;

fn main() {
	let mut s = String::new();
	std::io::stdin().read_to_string(&mut s).ok();

	let s: String = s.trim().replace("\n", "");

	for i in 1..s.len() {
		if s.chars().nth(i - 1) == s.chars().nth(i) {
			println!("No");
			return;
		}
	}
	println!("Yes");
}