#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <map>
#include <stack>
using namespace std;
bool A[10101];

int main()
{
	int n; cin >> n;
	vector<vector<int>>X(10101);
	vector<int>rc;
	for (int i = 0; i < n; i++) {
		int r0, r1, c0, c1;
		cin >> r0 >> c0 >> r1 >> c1;
		rc.push_back(r0 * 100 + c0);rc.push_back(r1 * 100 + c1);
		X[r0 * 100 + c0].push_back(r1 * 100 + c1);
		X[r1 * 100 + c1].push_back(r0 * 100 + c0);
	}

	stack<int>st;

	int cnt = 0;
	for (int j = 0; j < 2*n; j++) {
		if (A[rc[j]])continue;
		st.push(rc[j]);
		vector<int>B(10101);
		for (int i = 0; i < 10101; i++)B[i] = 1000;
		B[rc[j]] = 0;
		while (!st.empty() && cnt < 2) {
			int p = st.top(); st.pop();
			if (A[p]) {
				cnt++;
				continue;
			}
			A[p] = true;
			cout << p << endl;
			for (int i = 0; i < X[p].size(); i++) {
				if (B[X[p][i]] == B[p] - 1)continue;
				if (!A[X[p][i]]) {
					B[X[p][i]] = B[p] + 1;
					st.push(X[p][i]);
				}
				else{
					cnt++;
				}
			}
		}
	}

	if (cnt<2)cout << "YES" << endl;
	else cout << "NO" << endl;

    return 0;
}