#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<int, int>;

int main() {
    vector<P> v(6);
    for(int i=0; i<6; ++i) {
        cin >> v[i].first >> v[i].second;
        if(v[i].first > v[i].second) {
            swap(v[i].first, v[i].second);
        }
    }
    sort(v.begin(), v.end());
    if(v[0] != v[1] || v[2] != v[3] || v[4] != v[5] || v[0].first != v[2].first || v[0].second != v[4].first || v[2].second != v[4].second) {
        cout << "no" << endl;
    } else {
        cout << "yes" << endl;
    }
}
