using System;
using System.Collections.Generic;
using static Assistant.Input;
using static Assistant.Debug;
using System.Linq;
using Assistant;

namespace AGC014B
{
    class Program
    {
        static void Main(string[] args)
        {
            var N = ReadInt;
            var M = ReadInt;

            Dictionary<int, int> dic = new Dictionary<int, int>();
            for (int i = 0; i < M; i++)
            {
                int a = ReadInt;
                int b = ReadInt;

                if (dic.ContainsKey(a))
                {
                    int c = dic[a];
                    if (dic.ContainsKey(b) && dic[b] == a)
                    {
                        dic.Remove(a);
                        dic.Remove(b);
                    }
                    else if (dic.ContainsKey(b))
                    {
                        int d = dic[b];
                        dic[c] = d;
                        dic[d] = c;
                        dic.Remove(a);
                        dic.Remove(b);
                    }
                    else
                    {
                        dic[c] = b;
                        dic.Add(b, c);
                        dic.Remove(a);
                    }
                }
                else if (dic.ContainsKey(b))
                {
                    int c = dic[b];
                    dic[c] = a;
                    dic.Add(a, c);
                    dic.Remove(b);
                }
                else
                {
                    dic.Add(a, b);
                    dic.Add(b, a);
                }
            }

            if (dic.Count == 0) Console.WriteLine("YES");
            else Console.WriteLine("NO");
        }


    }


}

namespace Assistant
{
    static class Input
    {
        static List<string> line = new List<string>();
        static int index = 0;
        static String ReadNext()
        {
            if (line.Count <= index) line.AddRange(Console.ReadLine().Split());
            return line[index++];
        }
        public static int ReadInt => int.Parse(ReadNext());
        public static long ReadLong => long.Parse(ReadNext());
        public static int[] ReadInts => Console.ReadLine().Split().Select(int.Parse).ToArray();
        public static long[] NextLongs => Console.ReadLine().Split().Select(long.Parse).ToArray();
    }

    static class Debug
    {
        static public void Draw2D(int[,] map, int mode = 1)
        {
#if DEBUG
            int W = map.GetLength(0);
            int H = map.GetLength(1);

            int[,] map2 = new int[W + 1, H + 1];
            for (int i = 0; i < W + 1; i++)
            {
                for (int j = 0; j < H + 1; j++)
                {
                    if (i == 0 && j == 0) map2[i, j] = 0;
                    else if (i == 0) map2[i, j] = j - 1;
                    else if (j == 0) map2[i, j] = i - 1;
                    else map2[i, j] = map[i - 1, j - 1];
                }
            }

            for (int i = 0; i < W + 1; i++)
            {
                for (int j = 0; j < H + 1; j++)
                {
                    if (mode == 0) Console.Write(map2[i, j] % 10);
                    if (mode == 1) Console.Write(map2[i, j] + " ");
                }
                Console.WriteLine();
            }
            Console.WriteLine();
#endif
        }

        static void Draw1D(int[] array, int mode = 0)
        {
#if DEBUG
            Console.WriteLine(string.Join(" ", array));
#endif
        }
    }
}


Measured memory_bytes: 46296