#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(ll i=0;i<n;i++)
#define repl(i,l,r) for(ll i=(l);i<(r);i++)
#define per(i,n) for(ll i=(n)-1;i>=0;i--)
#define perl(i,r,l) for(ll i=r-1;i>=l;i--)
#define fi first
#define se second
#define pb push_back
#define ins insert
#define pqueue(x) priority_queue<x,vector<x>,greater<x>>
#define all(x) (x).begin(),(x).end()
#define CST(x) cout<<fixed<<setprecision(x)
#define rev(x) reverse(x);
using ll=long long;
using vl=vector<ll>;
using vvl=vector<vector<ll>>;
using pl=pair<ll,ll>;
using vpl=vector<pl>;
using vvpl=vector<vpl>;
const ll MOD=1000000007;
const ll MOD9=998244353;
const int inf=2e9+1;
const ll INF=4e18;
const ll dy[8]={-1,0,1,0,1,1,-1,-1};
const ll dx[8]={0,-1,0,1,1,-1,1,-1};
template <typename T> inline bool chmax(T &a, T b) {
  return ((a < b) ? (a = b, true) : (false));
}
template <typename T> inline bool chmin(T &a, T b) {
  return ((a > b) ? (a = b, true) : (false));
}
ll n;
vector<vl> g(20000);
vector<bitset<20000>> bs(20000);//2->1
void dfs(ll v,ll par=-1,ll dep=0){
  if(dep==2){
    if(par==0||v==0)return;
    bs[v].set(par);
    return;
  }
  for(auto p:g[v]){
    if(p==par)continue;
    dfs(p,v,dep+1);
  }
}
int main(){
  cin >> n;
  ll m;cin >> m;
  vl x(m),y(m);
  rep(i,m){
    ll a,b;cin >> a >> b;a--;b--;
    x[i]=a;y[i]=b;
    g[a].emplace_back(b);
    g[b].emplace_back(a);
  }
  dfs(0);
  /*rep(i,n){
    rep(j,n)cout << bs[i][j];cout << endl;
  }*/
  rep(i,m){
    if(x[i]==0||y[i]==0)continue;
    auto dp=bs[x[i]]|bs[y[i]];
    //dp.set(0,0);
    dp.set(x[i],0);
    dp.set(y[i],0);
    if(dp.count()>1){
      cout << "YES" << endl;return 0;
    }
  }
  cout << "NO" << endl;
}