use std::collections::HashSet;


fn main() {
    let mut nm = String::new();
    std::io::stdin().read_line(&mut nm).ok();
    let nm: Vec<usize> = nm.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
    let n = nm[0];
    let m = nm[1];
    let mut paths = vec![vec![]; n];
    for _ in 0..m {
        let mut temp = String::new();
        std::io::stdin().read_line(&mut temp).ok();
        let temp: Vec<usize> = temp.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
        let a = temp[0]-1;
        let b = temp[1]-1;
        paths[a].push(b);
        paths[b].push(a);
    }

    let mut used = HashSet::new();
    for &u in paths[0].iter() {
        for &v in paths[u].iter() {
            used.insert(v);
        }
    }
    used.remove(&0);
    for &u in used.iter() {
        for &v in paths[u].iter() {
            if used.contains(&v) {
                println!("YES");
                return;
            }
        }
    }
    println!("NO");
}