import java.util.*;

public class Main {
  static int[] par;
  static int[] rank;

  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int m = sc.nextInt();
    par = new int[n];
    rank = new int[n];
    for(int i = 0; i < n; i++) {
      par[i] = i;
      rank[i] = 0;
    }
    int kiten = 0;
    int[] e = new int[n];
    for(int i = 0; i < m; i++) {
      int a = sc.nextInt();
      int b = sc.nextInt();
      e[a]++;
      e[b]++;
      unite(a, b);
    }
    for(int i = 0; i < n; i++) {
      if(e[i] % 2 == 1) kiten++;
    }
    int count = 0;
    for(int i = 0; i < n; i++) {
      for(int j = i + 1; j < n; j++) {
        if((e[i] > 0) && (e[j] > 0)) {
          if(!same(i, j)) count++;
        }
      }
    }
    String ans = "NO";
    if((count == 0) && ((kiten == 0) || (kiten == 2))) ans = "YES";
    System.out.println(ans);
  }

  public static int find(int x) {
    if(par[x] == x) {
      return x;
    } else {
      return par[x] = find(par[x]);
    }
  }

  public static void unite(int x, int y) {
    x = find(x);
    y = find(y);
    if(rank[x] < rank[y]) {
      par[x] = y;
    } else {
      par[y] = x;
      if(rank[x] == rank[y]) rank[x]++;
    }
  }

  public static boolean same(int x, int y) {
    return find(x) == find(y);
  }
}