#include <bits/stdc++.h>
using namespace std;
int main() {
  pair<int, int> pa;
  vector<pair<int, int> > vepa;
  int a, b, ch[1001] = {0}, k;
  for (int i = 0; i < 6; i++) {
    cin >> a >> b;
    if (a < b) {
      pa.first = a;
      pa.second = b;
    } else {
      pa.first = b;
      pa.second = a;
    }
    vepa.push_back(pa);
  }
  sort(vepa.begin(), vepa.end());
  k = 0;
  if (vepa[0] == vepa[1] && vepa[2] == vepa[3] && vepa[4] == vepa[5]) {
    ch[vepa[0].first]++;
    ch[vepa[2].first]++;
    ch[vepa[4].first]++;
    ch[vepa[0].second]++;
    ch[vepa[2].second]++;
    ch[vepa[4].second]++;
    for (int i = 0; i <= 1000; i++) {
      if (ch[i] % 2 != 0) k++;
    }
    if (k == 0)
      cout << "yes" << endl;
    else
      cout << "no" << endl;
  } else {
    cout << "no" << endl;
  }
  return 0;
}
