# include <iostream>
# include <algorithm>
# include <vector>
# include <string>
# include <set>
# include <map>
# include <cmath>
# include <iomanip>
# include <tuple>
# include <functional>
# include <utility>
# define INF 1000000000
# define MOD 1000000000+7
using namespace std;

int main() {
	pair< int, int > Q[6];
	for (int i = 0; i < 6; i++) {
		cin >> Q[i].first >> Q[i].second;
		if (Q[i].first > Q[i].second) swap(Q[i].first, Q[i].second);
	}
	sort(Q, Q + 6);

	if (Q[0] == Q[1] && Q[2] == Q[3] && Q[4] == Q[5] && Q[0].first == Q[2].first&&Q[2].second == Q[4].second && Q[0].second == Q[4].first) {
		cout << "yes" << endl;
	}
	else {
		cout << "no" << endl;
	}
}