#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[20001];

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);
	}
	rep(i,0,N) {
		for (int a: E1[i]) {
			for (int b: E1[a]) {
				if (b==i) continue;
				E2[i].pb(mp(a,b));
			}
		}
	}
	rep(a1,0,N) {
		for (Pii x: E2[a1]) {
			int a2 = x.first;
			int a3 = x.second;
			for (Pii y: E2[a3]) {
				int b2 = y.first;
				int b3 = y.second;
				if (a1==b2 || a1==b3) continue;
				if (a2==b2 || a2==b3) continue;
				for (int z: E1[b3]) {
					//printf("a1=%d a2=%d a3=%d b2=%d b3=%d z=%d\n",a1,a2,a3,b2,b3,z);
					if (z==a1) {
						cout << "YES" << endl;
						return 0;
					}
				}
			}
		}
	}
	cout << "NO" << endl;
	return 0;
}