use std::collections::HashMap;


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 ab = String::new();
        std::io::stdin().read_line(&mut ab).ok();
        let ab: Vec<usize> = ab.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
        let a = ab[0]-1;
        let b = ab[1]-1;
        paths[a].push(b);
        paths[b].push(a);
    }

    let mut mapping = vec![vec![]; n];
    for &u in paths[0].iter() {
        for &v in paths[u].iter() {
            mapping[v].push(u);
        }
    }
    for i in 0..n {
        if mapping[i].is_empty() { continue; }
        for j in i+1..n {
            if mapping[j].is_empty() { continue; }
            if mapping[i].len() > 2 && mapping[j].len() > 2 {
                println!("YES");
                return;
            } else {
                for &k in mapping[i].iter() {
                    for &l in mapping[j].iter() {
                        if k != j && k != l && l != i {
                            println!("YES");
                            return;
                        }
                    }
                }
            }
        }
    }
    println!("NO");
}