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
    };
    if is_possible(&graph) {
        println!("YES");
    } else {
        println!("NO");
    }
}

fn is_possible(graph: &Vec<Vec<usize>>) -> bool {
    let nodes = {
        let mut nodes = vec![vec![]; graph.len()];
        for &ni in &graph[0] {
            for &nj in &graph[ni] {
                if nj != 0 {
                    nodes[nj].push(ni);
                }
            }
        }
        nodes
    };
    for ni in 0..graph.len() {
        for &nj in &graph[ni] {
            if nodes[ni].len() == 0 || nodes[nj].len() == 0 {
                continue;
            }
            if nodes[ni].len().min(nodes[nj].len()) >= 3 {
                return true;
            }
            for &nk in &nodes[ni] {
                if nk != nj {
                    for &nl in &nodes[nj] {
                        if nl != ni && nl != nk {
                            return true;
                        }
                    }
                }
            }
        }
    }
    false
}