#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int INF = 1e9;
const ll LINF = 1e18;
inline ll gcd(ll a, ll b) { return b ? gcd(b, a%b) : a; }
inline ll lcm(ll a, ll b) { return a / gcd(a, b)*b; }
template<class S,class T> ostream& operator << (ostream& out,const pair<S,T>& o){ out << "(" << o.first << "," << o.second << ")"; return out; }
template<class T> ostream& operator << (ostream& out,const vector<T> V){ for(int i = 0; i < V.size(); i++){ out << V[i]; if(i!=V.size()-1) out << " ";} return out; }
template<class T> ostream& operator << (ostream& out,const vector<vector<T> > Mat){ for(int i = 0; i < Mat.size(); i++) { if(i != 0) out << endl; out << Mat[i];} return out; }
template<class S,class T> ostream& operator << (ostream& out,const map<S,T> mp){ out << "{ "; for(auto it = mp.begin(); it != mp.end(); it++){ out << it->first << ":" << it->second; if(mp.size()-1 != distance(mp.begin(),it)) out << ", "; } out << " }"; return out; }

/*
 <url:https://yukicoder.me/problems/no/408>
 問題文============================================================
 =================================================================
 解説=============================================================
 ================================================================
 */

bool rec(int n,int dep,vector<int>& flag,vector<vector<int>>& G){
    if(flag[n]){
        if(n != 0) return false;
        else {
            if(dep == 5){
                return true;
            }
            else return false;
        }
    }
    if(dep >= 5) return false;
    flag[n] = true;
    for(auto next:G[n]){
        if(rec(next,dep+1,flag,G)) return true;
    }
    return false;
}
string solve(){
    int N,M; cin >> N >> M;
    vector<vector<int>> G(N);
    for(int i = 0; i < M;i++){
        int A,B; cin >> A >> B;
        A--; B--;
        G[A].push_back(B);
        G[B].push_back(A);
    }
    
    vector<int> flag(N);
    if(rec(0,0,flag,G)) return "YES";
    else return "NO";
}
int main(void) {
    cin.tie(0); ios_base::sync_with_stdio(false);
    cout << solve() << endl;
    return 0;
}