fn dfs(cur: usize, paths: &Vec<Vec<usize>>, cnt: &mut usize, checked: &mut Vec<bool>) -> bool {
    if checked[cur] {
        return cur == 0 && *cnt >= 5;
    }
    checked[cur] = true;
    *cnt += 1;
    for &v in paths[cur].iter() {
        if dfs(v, &paths, cnt, checked) {
            return true;
        }
    }
    checked[cur] = false;
    *cnt -= 1;
    false
}

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 checked = vec![false; n];
    let mut cnt = 0usize;
    if dfs(0, &paths, &mut cnt, &mut checked) {
        println!("YES");
    } else {
        println!("NO");
    }
}