#include <bits/stdc++.h>
#define ll long long
#define INF 1000000005
#define MOD 1000000007
#define EPS 1e-10
#define rep(i,n) for(int i=0;i<(int)n;++i)
#define each(a, b) for(auto (a): (b))
#define all(v) (v).begin(),(v).end()
#define fi first
#define se second
#define pb push_back
#define show(x) cout <<#x<<" = "<<(x)<<endl
#define spair(p) cout <<#p<<": "<<p.fi<<" "<<p.se<<endl
#define svec(v) cout<<#v<<":";rep(kbrni,v.size())cout<<" "<<v[kbrni];cout<<endl
#define sset(s) cout<<#s<<":";each(kbrni,s)cout <<" "<<kbrni;cout<<endl

using namespace std;

typedef pair<int,int>P;

const int MAX_N = 20005;

vector<int> G[MAX_N];
vector<int> vec[MAX_N];

void search(int u,int p,int depth)
{
    if(depth == 2){
        vec[u].pb(p);
    }else{
        rep(i,G[u].size()){
            if(G[u][i] != p){
                search(G[u][i],u,depth+1);
            }
        }
    }
}

int main()
{
    int n,m;
    cin >> n >> m;
    rep(i,m){
        int a,b;
        cin >> a >> b;
        G[a-1].pb(b-1);
        G[b-1].pb(a-1);
    }
    rep(i,n){
        sort(all(G[i]));
    }
    search(0,-1,0);
    rep(i,n){
        sort(all(vec[i]));
    }
    rep(i,n){
        rep(j,vec[i].size()){
            for(int k=i+1;k<n;k++){
                int cnt = upper_bound(all(G[i]),k)-lower_bound(all(G[i]),k);
                if(cnt >= 1){
                    auto it1 = lower_bound(all(vec[k]),vec[i][j]);
                    auto it2 = upper_bound(all(vec[k]),vec[i][j]);
                    if(it1 != vec[k].begin() || it2 != vec[k].end()){
                        cout << "YES\n";
                        return 0;
                    }
                }
            }
        }
    }
    cout << "NO\n";
    return 0;
}