#include <bits/stdc++.h>
using namespace std;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;
typedef unsigned long long ull;

#define MAX_V 305
int V;
vector<int> G[MAX_V];
int match[MAX_V];
bool used[MAX_V];

void init_graph(){
  for(int i=0; i<MAX_V; i++){
    G[i].clear();
    match[i] = -1;
    used[i] = false;
  }
}
void add_edge(int u, int v){
  G[u].push_back(v);
  G[v].push_back(u);
}
bool dfs(int v){
  used[v] = true;
  for(int i=0; i<G[v].size(); i++){
    int u = G[v][i], w = match[u];
    if(w<0||!used[w]&&dfs(w)){
      match[v] = u;
      match[u] = v;
      return true;
    }
  }
  return false;
}
int bipartite_matching(){
  int res = 0;
  rep(i,MAX_V) match[i] = -1;
  for(int v=0; v<V; v++){
    if(match[v] < 0){
      rep(i,MAX_V) used[i] = false;
      if(dfs(v)){
        res++;
      }
    }
  }
  return res;
}

int main(){
  int N;
  cin >> N;
  int n = 0;
  map<pair<int,int>,int> vertex;
  vector< pair<int,int> > edge;
  rep(i,N){
    int a, b, c, d;
    cin >> a >> b >> c >> d;
    if(vertex.count(make_pair(a,b)) == 0) vertex[make_pair(a,b)] = n++;
    if(vertex.count(make_pair(c,d)) == 0) vertex[make_pair(c,d)] = n++;
    int va = vertex[make_pair(a,b)];
    int vb = vertex[make_pair(c,d)];

    edge.push_back(make_pair(va,vb));
  }
  V = n + edge.size();
  
  rep(i,edge.size()){
    int e = n+i;
    int va = edge[i].first;
    int vb = edge[i].second;

    add_edge(e,va);
    add_edge(e,vb);
  }

  int ret = bipartite_matching();
  if(ret == edge.size()) cout << "YES" << endl;
  else cout << "NO" << endl;
  
  return 0;
}