use std::io::Read;

fn main() {
	let mut s = String::new();
	std::io::stdin().read_to_string(&mut s).ok();
	let s: Vec<_> = s.replace('\n', "").chars().collect();
	let a = s.windows(2).all(|w| w[0] != w[1]);
	println!("{}", if a { "Yes" } else { "No" });
}