#include <bits/stdc++.h>
using namespace std;
int main() {
  int h, w, s = 0, t = 0;
  int a[1000][1000] = {};
  for (int i = 0; i < 6; i++) {
    cin >> h >> w;
    if (h < w) {
      int tmp = h;
      h = w;
      w = tmp;
    }
    a[h][w]++;
  }
  for (int i = 0; i < 1000; i++) {
    for (int j = 0; j < 1000; j++) {
      if (a[i][j] == 2) t++;
      if (a[i][j] == 4) s++;
    }
  }
  if (t == 1 && s == 1)
    cout << "yes" << endl;
  else
    cout << "no" << endl;
}
