#include <bits/stdc++.h>
using namespace std;
const int INF = 1e9;
const long long LINF = 1e18;
const long long MOD = 1e9 + 7;
double EPS = 1e-8;
int main() {
  map<pair<int, int>, int> m;
  for (int i = (0); i < (int)(6); i++) {
    int a, b;
    cin >> a >> b;
    if (a > b) swap(a, b);
    m[{a, b}]++;
  }
  for (auto& p : m)
    if (p.second & 1) {
      cout << "no" << endl;
      return 0;
    }
  cout << "yes" << endl;
}
