#include <iostream>
#include <string>
#include <algorithm>
#include <functional>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <bitset>
#include <map>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
using namespace std;
typedef long long ll;
typedef pair<int,int> pint;
typedef vector<int> vint;
typedef vector<pint> vpint;
#define mp make_pair
#define fi first
#define se second
#define all(v) (v).begin(),(v).end()
#define rep(i,n) for(int i=0;i<(n);i++)
#define reps(i,f,n) for(int i=(f);i<(n);i++)
int n, m;
vector<int> g[20010];
bool memo[20010][20010];

int main(void){
    cin >> n >> m;
    rep(i, m){
        int a, b; cin >> a >> b;
        a--; b--;
        g[a].push_back(b);
        g[b].push_back(a);
        memo[a][b] = memo[b][a] = true;
    }


    //1 - u - vとなるような辺を見つける
    vector<pair<int, int> > d;
    for(int u : g[0]){
        for (int v : g[u]){
            //頂点に戻るようなものは入れない
            if(v != 0) d.push_back(make_pair(u, v));
        }
    }

    for (int i = 0; i < d.size() - 1; ++i){
        for (int j = i + 1; j < d.size(); ++j){
            if(d[i].first  != d[j].first && d[i].first  != d[j].second && 
               d[i].second != d[j].first && d[i].second != d[j].second){
                /*
                for (int tmp : g[d[i].second]){
                    if(tmp == d[j].second){
                        printf("YES\n");
                        return 0;
                    }
                }
                */
                if(memo[d[i].second][d[j].second]){
                    printf("YES\n");
                    return 0;
                }
            }
        }
    }
    printf("NO\n");
    return 0;
}