#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
map<pair<int, int>, int> gogo;
vector<int> vertexs[10000];
int not_be_connect[10000] = {};
int visited[10000] = {};
int now_cnt = 1;
int main() {
	int n;
	cin >> n;
	for (int i = 0;i < n;++i) {
		int a[2], b[2];
		cin >> a[0] >> b[0] >> a[1] >> b[1];
		for (int q = 0;q < 2;++q) {
			if (gogo[make_pair(a[q], b[q])] == 0) {
				gogo[make_pair(a[q], b[q])] = now_cnt;
				now_cnt++;
			}
		}
		vertexs[gogo[make_pair(a[0], b[0])]].push_back(gogo[make_pair(a[1], b[1])]);
		vertexs[gogo[make_pair(a[1], b[1])]].push_back(gogo[make_pair(a[0], b[0])]);
	}
	int cnt = 1;
	while (cnt != 0) {
		cnt = 0;
		for (int i = 1;i < now_cnt;++i) {
			if (not_be_connect[i] == false) {
				int nya = 0;
				for (int j = 0;j < vertexs[i].size();++j) {
					if (not_be_connect[vertexs[i][j]] == false) nya++;
				}
				if (nya <= 1) {
					not_be_connect[i] = true;
					cnt++;
				}
			}
		}
	}
	for (int i = 1;i < now_cnt;++i) {
		if (visited[i] == false && not_be_connect[i] == false) {
			visited[i] = true;
			queue<int> gooo;
			gooo.push(i);
			while (gooo.empty() == false) {
				int hooo = gooo.front();
				gooo.pop();
				int nya = 0;
				for (int j = 0;j < vertexs[hooo].size();++j) {
					if (not_be_connect[vertexs[hooo][j]] == false) {
						nya++;
						if (visited[vertexs[hooo][j]] == false) {
							visited[vertexs[hooo][j]] = true;
							gooo.push(vertexs[hooo][j]);
						}
					}
				}
				if (nya >= 3) {
					cout << "NO" << endl;
					return 0;
				}
			}
		}
	}
	cout << "YES" << endl;
}