#define _CRT_SECURE_NO_WARNINGS // #pragma warning(disable:4996)
#include <iostream>
#include <cstdio>
#include <algorithm>
#include <vector>
#include <string>
#include <queue>
#include <functional>
#include <sstream>
#include <cmath>
#include <set>
#include <map>
using namespace std; 

#define rep(i,a,b) for(int i=(a);i<(b);i++)
#define pb push_back
#define mp(a,b) make_pair(a,b)
#define all(a) a.begin(),a.end()
#define len(x) ((int)(x).size())
#define tmax(a,b,c) max((a),max((b),(c)))
#define debug(x) cerr << #x << " is " << x << endl;

typedef pair<int, int> Pii;
typedef vector<int> V;
typedef vector<vector<int> > VV;
typedef long long ll;
const int inf = 2e9;
const int mod = 1e9 + 7;
const long double eps = 1e-10;

int N, M;
V E1[20001];
vector<Pii> E2;

int main()
{
	cin >> N >> M;
	rep(i,0,M) {
		int a, b; cin >> a >> b;
		a--; b--;
		E1[a].pb(b);
		E1[b].pb(a);
	}

	for (int b: E1[0]) {
		for (int c: E1[b]) {
			if (c==0) continue;
			E2.pb(mp(b,c));
		}
	}

	rep(i,0,len(E2)-1) {
		rep(j,i,len(E2)) {
			int b = E2[i].first;
			int c = E2[i].second;
			int d = E2[j].second;
			int e = E2[j].first;
			if (b==d || b==e || c==d || c==e) continue;
			for (auto x: E1[c]) {
				if (x==d) {
					cout << "YES" << endl;
					return 0;
				}
			}
		}
	}

	cout << "NO" << endl;
	return 0;
}