#include <iostream>
using namespace std;

struct iostream_init_struct
{ 
	iostream_init_struct()
	{
		std::cin.tie(0);
		std::cin.sync_with_stdio(false);
	}
} iostream_init;

#include <unordered_map>
template <class TYPE, class TYPE_HASH>
class union_find
{
private:
	std::unordered_map<TYPE, TYPE, TYPE_HASH> parent_;
	std::unordered_map<TYPE, int, TYPE_HASH> loop_;
public:
	TYPE find(TYPE x)
	{
		auto itr = parent_.find(x);
		if (itr == parent_.end())
			return x;
		else
		{
			TYPE parent = itr->second;
			return parent_[x] = find(parent);
		}
	}
	// returns num of loop
	int unite(TYPE x, TYPE y)
	{
		TYPE x_parent = find(x);
		TYPE y_parent = find(y);
		if (x_parent == y_parent)
		{
			return loop_[x_parent] += 1;
		}
		parent_[y_parent] = x_parent;

		int ret = loop_[x_parent] += loop_[y_parent];
		loop_.erase(y_parent);
		return ret;
	}
	bool is_same(TYPE x, TYPE y)
	{
		return find(x) == find(y);
	}
};

class PairHash
{
public:
	size_t operator()(const pair<int, int>& obj) const
	{
		return obj.first * 1000 + obj.second;
	}
};

int main(void)
{
	union_find<pair<int, int>, PairHash> m;
	int N;
	cin >> N;
	for (int i = 0; i < N; ++i)
	{
		int r0, c0, r1, c1;
		cin >> r0 >> c0 >> r1 >> c1;
		if (m.unite(make_pair(r0, c0), make_pair(r1, c1)) >= 2)
		{
			cout << "NO" << endl;
			return 0;
		}
	}
	cout << "YES" << endl;
	return 0;
}