fn main() {
    proconio::input! {
        n: usize,
        m: usize,
        ab: [(usize, usize); m],
    }
    let graph = {
        let mut g = vec![vec![]; n];
        for (a, b) in ab {
            g[a - 1].push(b - 1);
            g[b - 1].push(a - 1);
        }
        g
    };
    let mut exists = vec![vec![false; n]; 6];
    exists[0][0] = true;
    for len in 1..=5 {
        for ni in 0..n {
            if !exists[len - 1][ni] {
                continue;
            }
            for &nj in &graph[ni] {
                exists[len][nj] = true;
            }
        }
    }
    if exists[5][0] {
        println!("YES");
    } else {
        println!("NO");
    }
}