#include <bits/stdc++.h>
using namespace std;
int main() {
  int b, c, i, a[1000][1000] = {0}, k = 0, j;
  for (i = 0; i < 6; i++) {
    cin >> b >> c;
    a[b][c]++;
    a[c][b]++;
  }
  for (i = 0; i < 1000; i++)
    for (j = 0; j < 1000; j++)
      if (a[i][j] % 2) k++;
  if (k)
    cout << "no" << endl;
  else
    cout << "yes" << endl;
}
