#include <iostream>
#include <iomanip>
#include <vector>
#include <algorithm>
#include <numeric>
#include <functional>
#include <cmath>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <sstream>
#include <string>
#define repd(i,a,b) for (int i=(int)(a);i<(int)(b);i++)
#define rep(i,n) repd(i,0,n)
#define all(x) (x).begin(),(x).end()
#define mod 1000000007
#define inf 2000000007
#define mp make_pair
#define pb push_back
typedef long long ll;
using namespace std;
template <typename T>
inline void output(T a, int p) {
    if(p) cout << fixed << setprecision(p)  << a << "\n";
    else cout << a << "\n";
}
// end of template

int main() {
    cin.tie(0);
    ios::sync_with_stdio(0);
    // source code
    int N, M;
    cin >> N >> M;
    vector<vector<int>> G(N);
    vector<int> H(N);
    rep(i, M){
        int a, b;
        cin >> a >> b;
        a--, b--;
        G[a].pb(b);
        G[b].pb(a);
    }
    vector<int> P(N, 0);
    for(int v: G[0]){
        P[v] = 1;
    }
    for(int i = 1; i < N; i++){
        for(int j: G[i]){
            for(int k: G[i]){
                if(k == j || k == 0) continue;
                for(int l: G[j]){
                    if(l == i || l == 0) continue;
                    if(P[k] && P[l]){
                        output("YES", 0);
                        return 0;
                    }
                }
            }
        }
    }
    
    output("NO", 0);
    
    
    return 0;
}