// use std::ops::{Index, IndexMut};
// use std::cmp::{Ordering, min, max};
// use std::collections::{BinaryHeap, BTreeMap};
// use std::collections::btree_map::Entry::{Occupied, Vacant};
// use std::clone::Clone;

fn getline() -> String{
    let mut res = String::new();
    std::io::stdin().read_line(&mut res).ok();
    res
}

macro_rules! readl {
    ($t: ty) => {
        {
            let s = getline();
            s.trim().parse::<$t>().unwrap()
        }
    };
    ($( $t: ty),+ ) => {
        {
            let s = getline();
            let mut iter = s.trim().split(' ');
            ($(iter.next().unwrap().parse::<$t>().unwrap(),)*) 
        }
    };
}

macro_rules! readlvec {
    ($t: ty) => {
        {
            let s = getline();
            let iter = s.trim().split(' ');
            iter.map(|x| x.parse().unwrap()).collect::<Vec<$t>>()
        }
    }
}

macro_rules! mvec {
    ($v: expr, $s: expr) => {
        vec![$v; $s]
    };
    ($v: expr, $s: expr, $($t: expr),*) => {
        vec![mvec!($v, $($t),*); $s]
    };
}

macro_rules! debug {
    ($x: expr) => {
        println!("{}: {:?}", stringify!($x), $x)
    }
}

fn printiter<'a, T>(v: &'a T)
where
    &'a T: std::iter::IntoIterator, 
    <&'a T as std::iter::IntoIterator>::Item: std::fmt::Display {
    for (i,e) in v.into_iter().enumerate() {
        if i != 0 {
            print!(" ");
        }
        print!("{}", e);
    }
    println!("");
}

type Cost = i64;

#[derive(Clone)]
struct Edge {
    to: usize,
    cost: Cost,
}

impl Ord for Edge {
    fn cmp(&self, other: &Edge) -> std::cmp::Ordering {
        (-self.cost).cmp(&(-other.cost))
    }
}

impl PartialOrd for Edge {
    fn partial_cmp(&self, other: &Edge) -> Option<std::cmp::Ordering> {
        Some(self.cmp(other))
    }
}

impl Eq for Edge {}

impl PartialEq for Edge {
    fn eq(&self, other: &Edge) -> bool {
        self.cost == other.cost
    }
}

#[derive(Clone)]
struct Graph {
    adj: Vec<Vec<Edge>>,
}

impl std::ops::Index<usize> for Graph {
    type Output = Vec<Edge>;

    fn index(&self, i: usize) -> &Vec<Edge> {
        &self.adj[i]
    }
}

impl std::ops::IndexMut<usize> for Graph {
    fn index_mut<'a>(&'a mut self, i: usize) -> &'a mut Vec<Edge> {
        &mut self.adj[i]
    }
}

impl Graph {

    fn new(n: usize) -> Graph{
        Graph {
            adj: vec![vec![]; n],
        }
    }

    fn size(&self) -> usize{
        self.adj.capacity()
    }

    fn add_edge(&mut self, from: usize, to_: usize, cost_: Cost) {
        self.adj[from].push(Edge{to: to_, cost: cost_});
    }

    fn add_uedge(&mut self, from: usize, to_: usize, cost_: Cost) {
        self.add_edge(from, to_, cost_);
        self.add_edge(to_, from, cost_);
    }

}


use std::collections::HashSet;

fn main() {
    let (n, m) = readl!(usize, usize); 
    let g = {
       let mut g = Graph::new(n);
       for _ in 0..m {
           let (a, b) = readl!(usize, usize);
           g.add_uedge(a-1, b-1, -1);
       }
       g
    };
    let mut pa = vec![HashSet::new(); n];
    for e1 in &g[0] {
        for e2 in &g[e1.to] {
            if e2.to != 0 {
                pa[e2.to].insert(e1.to);
            }
        }
    }
    // let pa: Vec<Vec<_>> = pa.into_iter().map(|s| {
    //     s.into_iter().collect()
    // }).collect();
    // debug!(pa);

    let mut f = false;
    for p in 0..n {
        for e in &g[p] {
            if pa[p].len() == 0 || pa[e.to].len() == 0 {
                continue;
            }
            if pa[p].len() < 3 && pa[e.to].len() < 3 {
                for ee in &pa[p] {
                    if *ee == e.to {
                        continue;
                    }
                    for eee in &pa[e.to] {
                        if *eee == p {
                            continue;
                        }
                        if *ee != *eee {
                            f = true;
                        }
                    }
                }
            } else {
                f = true;
            }
        }
    }
    if f {
        println!("YES");
    } else {
        println!("NO");
    }
}