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![HashSet::new(); 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].insert(b);
        paths[b].insert(a);
    }

    for &l1 in paths[0].iter() {
        for &r1 in paths[0].iter() {
            if l1 == r1 { continue; }
            for &l2 in paths[l1].iter() {
                if l2 == r1 || l2 == 0 { continue; }
                if paths[l2].intersection(&paths[r1]).any(|&v| v != 0 && v != l1) {
                    println!("YES");
                    return;
                }
            }
        }
    }
    println!("NO");
}