#include <bits/stdc++.h>
using namespace std;

int main(){
    int n, m, u, v;
    cin >> n >> m;
    vector<vector<int>> g(n);
    vector<pair<int,int>> edge(m);
    for(int i = 0; i < m; i++){
        cin >> u >> v;
        edge[i] = {--u, -- v};
        g[u].push_back(v);
        g[v].push_back(u);
    }
    vector<bool> used(n);
    for(auto &&u:g[0]){
        for(auto &&v:g[u]){
            used[v] = true;
        }
    }
    used[0] = false;
    for(int i = 0; i < m; i++){
        tie(u, v) = edge[i];
        if(used[u] && used[v]){
            cout << "YES" << '\n';
            return 0;
        }
    }
    cout << "NO" << '\n';
}