package No400番台;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		solver();
	}

	static void solver() {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int m = sc.nextInt();
		ArrayList<Integer>[] e = new ArrayList[n];
		for (int i = 0; i < n; i++) {
			e[i] = new ArrayList<>();
		}
		for (int i = 0; i < m; i++) {
			int a = sc.nextInt() - 1;
			int b = sc.nextInt() - 1;
			e[a].add(b);
			e[b].add(a);
		}
		boolean[] arrived=new boolean[n];
		dfs(0,0,arrived,0,e);
		System.out.println("NO");
	}
	static void dfs(int root, int p, boolean[] arrived, int depth, ArrayList<Integer>[] e) {
		if (depth == 4) {
			for (int v : e[p]) {
				if (root == v) {
					System.out.println("YES");
					System.exit(0);
				}
			}
		} else {
			for (int v : e[p]) {
				if (!arrived[v]) {
					boolean[] d = Arrays.copyOf(arrived, arrived.length);
					d[v] = true;
					dfs(root,v,d,depth+1,e);
				}
			}
		}
	}
}