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

public class UnionFind
{
    private int[] data;

    public UnionFind(int size)
    {
        data = new int[size];
        for (int i = 0; i < size; i++) data[i] = -1;
    }

    public bool Unite(int x, int y)
    {
        x = Root(x);
        y = Root(y);

        if (x != y)
        {
            if (data[y] < data[x])
            {
                var tmp = y;
                y = x;
                x = tmp;
            }
            data[x] += data[y];
            data[y] = x;
        }
        return x != y;
    }

    public bool IsSameGroup(int x, int y)
    {
        return Root(x) == Root(y);
    }

    private int Root(int x)
    {
        return data[x] < 0 ? x : data[x] = Root(data[x]);
    }
}

public class Hello
{
    public static void Main()
    {
        string[] line = Console.ReadLine().Trim().Split(' ');
        var n = int.Parse(line[0]);
        var m = int.Parse(line[1]);
        var a = new List<int>[n];
        for (int i = 0; i < n; i++) a[i] = new List<int>();
        var uf = new UnionFind(n);
        var start = 0;
        var getstart = false;
        for (int i = 1; i < m; i++)
        {
            line = Console.ReadLine().Trim().Split(' ');
            var s1 = int.Parse(line[0]);
            var s2 = int.Parse(line[1]);
            if (!getstart) { start = s1; getstart = true; }
            a[s1].Add(s2);
            a[s2].Add(s1);
            uf.Unite(s1, s2);
        }
        var count = 0;
        for (int i = 0; i < n; i++)
        {
            if (a[i].Count() > 0 && !uf.IsSameGroup(start, i)) { Console.WriteLine("NO"); goto end; }
            if (a[i].Count() % 2 == 1) count++;
        }
        if (!(count == 0 | count == 2)){ Console.WriteLine("NO"); goto end; }
        Console.WriteLine("YES");
        end:;
    }
}