#include using namespace std; #define rep(i,n) for(ll i=0;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,greater> #define all(x) (x).begin(),(x).end() #define CST(x) cout<; using vvl=vector>; using pl=pair; using vpl=vector; using vvpl=vector; 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 inline bool chmax(T &a, T b) { return ((a < b) ? (a = b, true) : (false)); } template inline bool chmin(T &a, T b) { return ((a > b) ? (a = b, true) : (false)); } ll n; vector g(20000); vector> 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; }