#include "stdafx.h"
#include<iostream>
#include<map>
#include<vector>
#include<algorithm>
using namespace std;
typedef pair<int, int> P;

int main() {
	vector<P>v;
	for (int i = 0;i < 6;i++) {
		int a, b;
		cin >> a >> b;
		v.push_back(make_pair(max(a, b), min(a, b)));
	}
	sort(v.begin(), v.end());

	if (v[0] == v[1] && v[2] == v[3] && v[4] == v[5]) {
		vector<int>num;
		for (int i = 0;i < 3;i++) {
			num.push_back(v[i * 2].first);
			num.push_back(v[i * 2].second);
		}
		sort(num.begin(), num.end());
		if (num[0] == num[1] && num[2] == num[3] && num[4] == num[5])cout << "yes" << endl;
		else cout << "no" << endl;
	}
	else cout << "no" << endl;
	return 0;
}