#include <iostream>
#include <utility>
#include <vector>
using namespace std;

int n;

vector<pair<int, int>> edges[111][111];

int visited[111][111];

int dfs(int r, int c, int prer = -1, int prec = -1) {
    if (visited[r][c] == 2) {
        return 0;
    } else if (visited[r][c] == 1) {
        return 1;
    }

    visited[r][c] = 1;

    int res = 0;

    for (auto& edge : edges[r][c]) {
        int tor = edge.first, toc = edge.second;

        if (prer == tor && prec == toc) continue;

        res += dfs(tor, toc, r, c);
    }

    visited[r][c] = 2;

    return res;
}

int main() {
    cin >> n;

    for (int i = 0; i < n; i++) {
        int r0, c0, r1, c1;
        cin >> r0 >> c0 >> r1 >> c1;

        edges[r0][c0].emplace_back(r1, c1);
        edges[r1][c1].emplace_back(r0, c0);
    }

    for (int i = 0; i < 101; i++) {
        for (int j = 0; j < 101; j++) {
            if (!visited[i][j]) {
                int res = dfs(i, j);

                if (res > 1) {
                    cout << "NO" << endl;
                    return 0;
                }
            }
        }
    }

    cout << "YES" << endl;
}