#include <bits/stdc++.h>
using namespace std;
int main() {
  int input[12];
  int h[6], w[6];
  for (int i = 0; i < 6; i++) {
    cin >> h[i] >> w[i];
    input[i * 2] = h[i];
    input[i * 2 + 1] = w[i];
  }
  sort(input, input + 12);
  bool flag = false;
  if (input[0] == input[3] && input[4] == input[7] && input[8] == input[11]) {
    cout << "yes" << endl;
  } else {
    cout << "no" << endl;
  }
  return 0;
}
