using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var c = NList;
        var (n, m) = (c[0], c[1]);
        var a = NList;
        var map = NArr(m);
        var small = new int[n + 1];
        var large = new int[n + 1];
        foreach (var edge in map)
        {
            if (edge[0] > edge[1])
            {
                if (small[edge[0]] == 0) small[edge[0]] = edge[1];
                else if (small[edge[0]] != edge[1])
                {
                    WriteLine("YES");
                    return;
                }
                if (large[edge[1]] == 0) large[edge[1]] = edge[0];
                else if (large[edge[1]] != edge[0])
                {
                    WriteLine("YES");
                    return;
                }
            }
            else if (edge[0] < edge[1])
            {
                if (large[edge[0]] == 0) large[edge[0]] = edge[1];
                else if (large[edge[0]] != edge[1])
                {
                    WriteLine("YES");
                    return;
                }
                if (small[edge[1]] == 0) small[edge[1]] = edge[0];
                else if (small[edge[1]] != edge[0])
                {
                    WriteLine("YES");
                    return;
                }
            }
        }
        WriteLine("NO");
    }
}