#include <bits/stdc++.h>
using namespace std;
__attribute__((constructor)) void initial() {
  cin.tie(0);
  ios::sync_with_stdio(false);
}
int main() {
  map<pair<int, int>, int> mp;
  for (int i = (0); i < (6); i++) {
    int h, w;
    cin >> h >> w;
    mp[pair<int, int>(min(h, w), max(h, w))]++;
  }
  for (auto x : mp) {
    if (x.second % 2 == 1) {
      cout << "no" << endl;
      return 0;
    }
  }
  cout << "yes" << endl;
}
