#include <bits/stdc++.h>
using namespace std;
struct Pair {
  int x;
  int y;
  bool paired;
};
void FndPair(Pair *p1, Pair *p2) {
  if ((p1->x == p2->x) && (p1->y == p2->y)) {
    p1->paired = true;
    p2->paired = true;
  }
}
int main() {
  Pair pair[6];
  for (int i = 0; i < 6; i++) {
    cin >> pair[i].x >> pair[i].y;
    if (pair[i].x > pair[i].y) swap(pair[i].x, pair[i].y);
    pair[i].paired = false;
  }
  for (int i = 0; i < 5; i++) {
    for (int j = i + 1; j < 6; j++) {
      if (pair[i].paired || pair[j].paired) continue;
      FndPair(&pair[i], &pair[j]);
    }
  }
  bool non_pair = false;
  for (int i = 0; i < 6; i++)
    if (!pair[i].paired) non_pair = true;
  if (non_pair)
    cout << "no" << endl;
  else
    cout << "yes" << endl;
  return 0;
}
