#include <bits/stdc++.h>
using namespace std;
int main() {
  int b, c, i, k = 0, l[1000] = {0}, m[1000] = {0};
  for (i = 0; i < 6; i++) {
    cin >> b >> c;
    if (b > c) {
      m[c]++;
      l[b]++;
    } else {
      m[b]++;
      l[c]++;
    }
  }
  for (i = 0; i < 1000; i++)
    if (m[i] % 4 || l[i] % 4) k++;
  if (k)
    cout << "no" << endl;
  else
    cout << "yes" << endl;
  return 0;
}
