#define  _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <algorithm>
#include <utility>
#include <functional>
#include <cstring>
#include <queue>
#include <stack>
#include <math.h>
#include <iterator>
#include <vector>
#include <string>
#include <set>
#include <math.h>
#include <iostream> 
#include<map>
#include <iomanip>
#include <stdlib.h>
#include <list>
#include <typeinfo>
#include <list>
#include <set>
using namespace std;
#define MAX_MOD 1000000007
#define REP(i,n) for(long long i = 0;i < n;++i)
#define LONG_INF 800000000000000000
vector<int> vertexs[200];
int can_be_ignored[200] = {};
map<pair<int, int>, vector<int>> hogee;
int already_visited[200] = {};
int main() {
	int n;
	cin >> n;
	for (int j = 0;j < n;++j) {
		int a[2], b[2];
		REP(i, 2) {
			cin >> a[i] >> b[i];
		}
		for (int i = 0;i < 2;++i) {
			for (int q = 0;q < hogee[make_pair(a[i], b[i])].size();++q) {
				vertexs[j].push_back(hogee[make_pair(a[i], b[i])][q]);
				vertexs[hogee[make_pair(a[i], b[i])][q]].push_back(j);
			}
			hogee[make_pair(a[i], b[i])].push_back(j);
		}
	}
	int cnt = 1;
	while (cnt != 0) {
		cnt = 0;
		for (int i = 0;i < n;++i) {
			if (can_be_ignored[i] == false) {
				int woww = 0;
				for (int q = 0;q < vertexs[i].size();++q) {
					if (can_be_ignored[vertexs[i][q]] == false) woww++;
				}
				if (woww <= 1) {
					can_be_ignored[i] = true;
					cnt++;
				}
			}
		}
	}
	for (int t = 0;t < n;++t) {
		if (already_visited[t] == false&&can_be_ignored[t] == false) {
			already_visited[t] = true;
			queue<int> ja;
			ja.push(t);
			while (ja.empty() == false) {
				int hogehoge = ja.front();
				int cnt = 0;
				for (int i = 0;i < vertexs[hogehoge].size();++i) {
					if (can_be_ignored[vertexs[hogehoge][i]] == false && already_visited[vertexs[hogehoge][i]] == 0) {
						cnt++;
						already_visited[vertexs[hogehoge][i]] = true;
						ja.push(vertexs[hogehoge][i]);
					}
				}
				if (cnt >= 2) {
					if (hogehoge != t|| cnt >= 3) {
						cout << "NO" << endl;
						return 0;
					}
				}
			}
		}
	}
	cout << "YES" << endl;
	return 0;
}