using System;
using System.Collections.Generic;
using System.Text;
using System.Linq;


class Program
{
    public void Proc()
    {
        Reader.IsDebug = false;
        int[] inpt = Reader.ReadLine().Split(' ').Select(a => int.Parse(a)).ToArray();

        int pointCount = inpt[0];
        int connectCount = inpt[1];

        for (int i = 0; i < connectCount; i++)
        {
            inpt = Reader.ReadLine().Split(' ').Select(a => int.Parse(a)).ToArray();
            if (!con.ContainsKey(inpt[0]))
            {
                con.Add(inpt[0], new Dictionary<int, bool>());
            }
            con[inpt[0]][inpt[1]] = true;
            if (!con.ContainsKey(inpt[1]))
            {
                con.Add(inpt[1], new Dictionary<int, bool>());
            }
            con[inpt[1]][inpt[0]] = true;
        }

        Dictionary<int, Dictionary<int, bool>> from1 = new Dictionary<int,Dictionary<int,bool>>();
        Dictionary<int, Dictionary<int, bool>> to1 = new Dictionary<int,Dictionary<int,bool>>();

        bool ans = false;
        if (con.ContainsKey(1))
        {
            foreach (int pos1 in con[1].Keys)
            {
                if (con.ContainsKey(pos1))
                {
                    foreach (int pos2 in con[pos1].Keys)
                    {
                        if (pos2 == 1)
                        {
                            continue;
                        }
                        if (!from1.ContainsKey(pos1))
                        {
                            from1.Add(pos1, new Dictionary<int, bool>());
                        }
                        from1[pos1][pos2] = true;
                        if (!to1.ContainsKey(pos2))
                        {
                            to1.Add(pos2, new Dictionary<int, bool>());
                        }
                        to1[pos2][pos1] = true;
                    }
                }
            }
            foreach (int pos1 in from1.Keys)
            {
                foreach (int pos2 in from1[pos1].Keys)
                {
                    foreach (int pos3 in from1.Keys)
                    {
                        if (pos1 == pos3 || pos2 == pos3)
                        {
                            continue;
                        }
                        foreach (int pos4 in from1[pos3].Keys)
                        {
                            if (pos1 == pos4 || pos2 == pos4)
                            {
                                continue;
                            }
                            if (con.ContainsKey(pos2) && con[pos2].ContainsKey(pos4))
                            {
                                ans = true;
                                break;
                            }
                        }
                        if (ans)
                        {
                            break;
                        }
                    }
                    if (ans)
                    {
                        break;
                    }
                }
                if (ans)
                {
                    break;
                }
            }
        }
        Console.WriteLine(ans ? "YES" : "NO");

    }


    private Dictionary<int, Dictionary<int, bool>> con = new Dictionary<int, Dictionary<int, bool>>();




    public class Reader
    {
        public static bool IsDebug = true;
        private static String PlainInput = @"





7 10
1 2
1 3
1 4
1 5
2 3
2 4
2 6
3 4
3 7
4 5





";
        private static System.IO.StringReader Sr = null;
        public static string ReadLine()
        {
            if (IsDebug)
            {
                if (Sr == null)
                {
                    Sr = new System.IO.StringReader(PlainInput.Trim());
                }
                return Sr.ReadLine();
            }
            else
            {
                return Console.ReadLine();
            }
        }
    }
    static void Main()
    {
        Program prg = new Program();
        prg.Proc();
    }
}