#include <cassert>
#include <iostream>
#include <vector>
#include <algorithm>
#include <utility>
#include <queue>

#define FOR(i, a, b) for (int i = (a); i < (b); i++)
#define RFOR(i, a, b) for (int i = (b)-1; i >= (a); i--)
#define rep(i, n) for (int i = 0; i < (n); i++)
#define rep1(i, n) for (int i = 1; i <= (n); i++)
#define rrep(i, n) for (int i = (n)-1; i >= 0; i--)

#define pb push_back
#define mp make_pair
#define fst first
#define snd second
#define show(x) cout << #x << " = " << x << endl
#define chmin(x, y) x = min(x, y)
#define chmax(x, y) x = max(x, y)
#define pii pair<int, int>
#define vi vector<int>

using namespace std;
template <class S, class T>
ostream& operator<<(ostream& o, const pair<S, T>& p)
{
    return o << "(" << p.first << "," << p.second << ")";
}
template <class T>
ostream& operator<<(ostream& o, const vector<T>& vc)
{
    o << "sz = " << vc.size() << endl
      << "[";
    for (const T& v : vc)
        o << v << ",";
    o << "]";
    return o;
}
typedef long long ll;

#define MAX 100
int N;
bool check[MAX][MAX];
vector<pii> edge[MAX][MAX];
int main()
{
    cin >> N;
    rep(i, N)
    {
        int r0, c0, r1, c1;
        cin >> r0 >> c0 >> r1 >> c1;
        r0--, c0--, r1--, c1--;
        edge[r0][c0].pb(mp(r1, c1));
        edge[r1][c1].pb(mp(r0, c0));
    }

    bool f = true;
    rep(i, MAX)
    {
        if (not f) {
            break;
        }
        rep(j, MAX)
        {
            if (not check[i][j]) {
                int v = 0;
                int e = 0;
                queue<pii> q;
                q.push(mp(i, j));
                check[i][j] = true;
                while (not q.empty()) {
                    const pii p = q.front();
                    v++;
                    q.pop();
                    for (const auto p2 : edge[p.fst][p.snd]) {
                        e++;
                        if (not check[p2.fst][p2.snd]) {
                            q.push(p2);
                            check[p2.fst][p2.snd] = true;
                        }
                    }
                }
                e /= 2;
                // if (e != 0) {
                //     cout << e << " " << v << endl;
                // }
                if (e > v) {
                    f = false;
                    break;
                }
            }
        }
    }
    if (f) {
        cout << "YES" << endl;
    } else {
        cout << "NO" << endl;
    }

    return 0;
}