#include <bits/stdc++.h>

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;
  }

}