import java.util.*;

public class Main {
	public static void main (String[] args) {
    	Scanner sc = new Scanner(System.in);
    	int n = sc.nextInt();
    	int m = sc.nextInt();
    	int[] counts = new int[n];
    	UnionFindTree uft = new UnionFindTree(n);
    	for (int i = 0; i < m; i++) {
    	    int a = sc.nextInt();
    	    int b = sc.nextInt();
    	    uft.unite(a, b);
    	    counts[a]++;
    	    counts[b]++;
    	}
   	    int count = 0;
    	for (int x : counts) {
    	    count += x % 2;
    	}
    	boolean flag = (count <= 2 && uft.isOne());
    	if (flag) {
    	    System.out.println("YES");
    	} else {
    	    System.out.println("NO");
    	}
    }
    
    static class UnionFindTree {
        int[] parents;
        int[] counts;
        
        public UnionFindTree(int size) {
            parents = new int[size];
            counts = new int[size];
            for (int i = 0; i < size; i++) {
                parents[i] = i;
                counts[i] = 1;
            }
        }
        
        public int find(int x) {
            if (x == parents[x]) {
                return x;
            } else {
                return parents[x] = find(parents[x]);
            }
        }
        
        public boolean same(int x, int y) {
            return find(x) == find(y);
        }
        
        public void unite(int x, int y) {
            if (!same(x, y)) {
                counts[find(y)] += counts[find(x)];
                counts[find(x)] = 0;
                parents[find(x)] = find(y);
            }
        }
        
        public boolean isOne() {
            int count = 0;
            for (int i = 0; i < counts.length; i++) {
                if (counts[i] > 1) {
                    count++;
                }
            }
            return count <= 1;
        }
    }
}