public class Main {
  private static void solve() {
    int n = ni();
    int m = ni();
    
    int[] rank = new int[n];
    UnionFind uf = new UnionFind(n);
    for (int i = 0; i < m; i ++) {
      int a = ni();
      int b = ni();
      rank[a] ++;
      rank[b] ++;
      uf.union(a, b);
    }
    
    int[] count = new int[2];
    for (int v : rank) {
      count[v % 2] ++;
    }
    int root = uf.find(0);
    for (int i = 0; i < n; i ++) {
      if (root != uf.find(i)) {
        System.out.println("NO");
        return;
      }
    }
    if (count[1] == 0 || count[1] == 2) {
      System.out.println("YES");
    } else {
      System.out.println("NO");
    }
  }
  
  static class UnionFind {
    private int[] table;
    private int[] rank;
    
    public UnionFind(int size) {
        this.table = new int[size];
        this.rank = new int[size];
        for (int i = 0; i < size; i ++) {
            this.table[i] = i;
            this.rank[i] = 1;
        }
    }

    public boolean isSame(int node1, int node2) {
        return find(node1) == find(node2);
    }

    public int find(int node) {
        if (table[node] == node) {
            return node;
        } else {
            return table[node] = find(table[node]);
        }
    }

    public void union(int node1, int node2) {
        int root1 = find(node1);
        int root2 = find(node2);
        
        if (rank[root1] < rank[root2]) {
            table[root1] = root2;
        } else if (rank[root1] > rank[root2]) {
            table[root2] = root1;
        } else if (root1 != root2) {
            table[root2] = root1;
            rank[root1] ++;
        }
    }
}
  public static void main(String[] args) {
    new Thread(null, new Runnable() {
      @Override
      public void run() {
        long start = System.currentTimeMillis();
        String debug = args.length > 0 ? args[0] : null;
        if (debug != null) {
          try {
            is = java.nio.file.Files.newInputStream(java.nio.file.Paths.get(debug));
          } catch (Exception e) {
            throw new RuntimeException(e);
          }
        }
        reader = new java.io.BufferedReader(new java.io.InputStreamReader(is), 32768);
        solve();
        out.flush();
        tr((System.currentTimeMillis() - start) + "ms");
      }
    }, "", 64000000).start();
  }

  private static java.io.InputStream is = System.in;
  private static java.io.PrintWriter out = new java.io.PrintWriter(System.out);
  private static java.util.StringTokenizer tokenizer = null;
  private static java.io.BufferedReader reader;

  public static String next() {
    while (tokenizer == null || !tokenizer.hasMoreTokens()) {
      try {
        tokenizer = new java.util.StringTokenizer(reader.readLine());
      } catch (Exception e) {
        throw new RuntimeException(e);
      }
    }
    return tokenizer.nextToken();
  }

  private static double nd() {
    return Double.parseDouble(next());
  }

  private static long nl() {
    return Long.parseLong(next());
  }

  private static int[] na(int n) {
    int[] a = new int[n];
    for (int i = 0; i < n; i++)
      a[i] = ni();
    return a;
  }

  private static char[] ns() {
    return next().toCharArray();
  }

  private static long[] nal(int n) {
    long[] a = new long[n];
    for (int i = 0; i < n; i++)
      a[i] = nl();
    return a;
  }

  private static int[][] ntable(int n, int m) {
    int[][] table = new int[n][m];
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        table[i][j] = ni();
      }
    }
    return table;
  }

  private static int[][] nlist(int n, int m) {
    int[][] table = new int[m][n];
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        table[j][i] = ni();
      }
    }
    return table;
  }

  private static int ni() {
    return Integer.parseInt(next());
  }

  private static void tr(Object... o) {
    if (is != System.in)
      System.out.println(java.util.Arrays.deepToString(o));
  }
}