#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];
vector<int> can_come_from[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);
	}
	for (int i = 0;i < path[1].size();++i) {
		for (int q = 0;q < path[path[1][i]].size();++q) {
			if (path[path[1][i]][q] != 1) {
				can_come_from[path[path[1][i]][q]].push_back(path[1][i]);
			}
		}
	}
	for (int i = 2;i <= n;++i) {
		if (can_come_from[i].size() != 0) {
			for (int q = 0;q < path[i].size();++q) {
				if (can_come_from[path[i][q]].size() != 0) {
					if (can_come_from[i] != can_come_from[q]) {
						cout << "YES" << endl;
						return 0;
					}
				}
			}
		}
	}
	cout << "NO" << endl;
	return 0;
}