#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <algorithm>
#include <utility>
#include <functional>
#include <cstring>
#include <queue>
#include <stack>
#include <math.h>
#include <iterator>
#include <vector>
#include <string>
#include <set>
#include <math.h>
#include <iostream> 
#include<map>
#include <stdlib.h>
#include <list>
#include <typeinfo>
#include <list>
#include <set>
#include <iomanip>
using namespace std;
#define MAX_MOD 1000000007
#define REP(i,n) for(int i = 0;i < n;++i)
vector<int> path[30000];
int have_come[10][30000] = {};
int main() {
	int n, m;
	cin >> n >> m;
	REP(i, m) {
		int a, b;
		cin >> a >> b;
		path[a].push_back(b);
		path[b].push_back(a);
	}
	queue<tuple<int,int,int>> hoge;
	hoge.push(make_tuple(1,1,0));
	while (hoge.empty() == false) {
		int now_here = get<0>(hoge.front());
		int before_come = get<1>(hoge.front());
		int score = get<2>(hoge.front());
		hoge.pop();
		if (score > 5) {//5を超えちゃった場合
			cout << "NO" << endl;
			return 0;
		}
		for (int i = 0;i < path[now_here].size();++i) {
			if (path[now_here][i] != before_come) {
				if (have_come[score+1][path[now_here][i]] == 0) {
					if (have_come[4 - score][path[now_here][i]] == 1) {
						cout << "YES" << endl;
						return 0;
					}
					have_come[score+1][path[now_here][i]] = true;
					hoge.push(make_tuple(path[now_here][i], now_here, score + 1));
				}
			}
		}
	}
	//そもそも道すらなかった場合
	cout << "NO" << endl;
	return 0;
}