#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, b;
  vector<pair<int, int>> rect;
  for (int i = 0; i < 6; i++) {
    cin >> a >> b;
    if (a > b) swap(a, b);
    bool c = false;
    for (int i = 0; i < rect.size(); i++) {
      if (rect[i].first == a && rect[i].second == b) {
        c = true;
        rect.erase(rect.begin() + i);
      }
    }
    if (!c) {
      rect.emplace_back(a, b);
    }
  }
  if (rect.size() == 0) {
    cout << "yes" << endl;
  } else {
    cout << "no" << endl;
  }
}
