#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;
int main() {
	vector<pair<int, int> > v(6);
	for (int i = 0; i < 6; i++) {
		cin >> v[i].first >> v[i].second;
		if (v[i].first > v[i].second) swap(v[i].first, v[i].second);
	}
	sort(v.begin(), v.end());
	if (v[0] != v[1] || v[2] != v[3] || v[4] != v[5]) cout << "no" << endl;
	else if (v[0].first != v[2].first || v[0].second != v[4].first || v[2].second != v[4].second) cout << "no" << endl;
	else cout << "yes" << endl;
	return 0;
}