#include<iostream>
#include<vector>
#include<map>

using namespace std;
typedef pair<int, int> pii;
map<pii, vector<pii>> g;
int N;
map<pii, int> used;
int x[101], y[101];

bool rec(int p, int q, int i, int j){

   used[pii(i, j)]=1;
   bool ret=true;
   for(pii z: g[pii(i, j)]){
      //cout<<p<<" "<<q<<" "<< i<<" "<<j<<" "<<z.first<<" "<<z.second<< endl;
      if(z.first==p&&z.second==q) continue;
      if(used[pii(z.first, z.second)]) return false;
      ret&=rec(i, j, z.first, z.second);
   }

   return ret;
}

int main(){

   cin>> N;
   for(int i=0; i<N; i++){
      int a, b, c, d;
      cin>> a>> b>> c>> d;
      //a--; b--; c--; d--;
      g[pii(a, b)].push_back(pii(c, d));
      g[pii(c, d)].push_back(pii(a, b));
      x[i]=a; y[i]=b;
   }

   bool ok=true;
   for(int i=0; i<N; i++){
      if(used[pii(x[i], y[i])]==1) continue;
      ok&=rec(-1, -1, x[i], y[i]);
   }

   if(ok){
      cout<< "YES"<< endl;
   }else{
      cout<< "NO"<< endl;
   }

   return 0;
}