#include <bits/stdc++.h>
using namespace std;
int main() {
  pair<int, int> a[6];
  for (int i = 0; i < 6; i++) {
    cin >> a[i].first >> a[i].second;
    if (a[i].first > a[i].second) {
      int tmp = a[i].first;
      a[i].first = a[i].second;
      a[i].second = tmp;
    }
  }
  sort(a, a + 6);
  set<int> s;
  if (a[0] == a[1]) {
    s.insert(a[0].first);
    s.insert(a[1].second);
    if (a[2] == a[3]) {
      s.insert(a[2].first);
      s.insert(a[3].second);
      if (a[4] == a[5]) {
        s.insert(a[4].first);
        s.insert(a[5].second);
        if (s.size() <= 3)
          cout << "yes\n";
        else
          cout << "no\n";
      } else
        cout << "no\n";
    } else
      cout << "no\n";
  } else
    cout << "no\n";
  return 0;
}
