#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, i;
  vector<pair<int, int> > v(6);
  for (i = 0; i < 6; i++) {
    scanf("%d%d", &v[i].first, &v[i].second);
    if (v[i].first > v[i].second) swap(v[i].first, v[i].second);
  }
  sort(v.begin(), v.end());
  puts(v[0] == v[1] && v[2] == v[3] && v[4] == v[5] ? "yes" : "no");
}
