//TODO
fn main() {
    let mut n = String::new();
    std::io::stdin().read_line(&mut n).ok();
    let n: usize = n.trim().parse().unwrap();
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    let s: &str = s.trim();

    if n == 1 {
        println!("NO");
    } else if n == 2 {
        if s == "00" || s == "11" {
            println!("YES");
        } else {
            println!("NO");
        }
    } else if n == 3 {
        if s == "010" || s == "101" {
            println!("NO");
        } else {
            println!("YES");
        }
    } else {
        println!("YES");
    }
}