#include "iostream"
#include "climits"
#include "list"
#include "queue"
#include "stack"
#include "set"
#include "functional"
#include "algorithm"
#include "math.h"
#include "utility"
#include "map"

using namespace std;
const long long int MOD = 1000000007;

typedef pair<int, int> P;
int N;
int place[111][111];
bool flag[111][111];
int a, b,c,d;
P current;
queue<P>Q;
int dx[4] = { 1,0,-1,0 };
int dy[4] = { 0,1,0,-1 };
int edge;
int node;

int main() {
	cin >> N;
	for (int i = 0; i < N; i++) {
		cin >> a >> b >> c >> d;
		place[a][b]++;
		place[c][d]++;
	}
	for (int i = 1; i < 101; i++) {
		for (int j = 1; j < 101; j++) {
			if (place[i][j]) {
				flag[i][j] = true;
			}
		}
	}
	for (int i = 1; i < 101; i++) {
		for (int j = 1; j < 101; j++) {
			if (flag[i][j]) {
				edge = place[i][j];
				node = 1;
				flag[i][j] = false;
				current.first = i;
				current.second = j;
				Q.push(current);
				while (!Q.empty()) {
					for (int k = 0; k < 4; k++) {
						current.first = Q.front().first + dy[k];
						current.second = Q.front().second + dx[k];
						if (flag[current.first][current.second]) {
							flag[current.first][current.second] = false;
							node++;
							edge += place[current.first	][current.second];
							Q.push(current);
						}
					}
					Q.pop();
				}
				if (edge / 2 > node) {
					cout << "NO\n";
					return 0;
				}
			}
		}
	}
	cout << "YES\n";
	return 0;
}