#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, n) for (ll i = 0; i < (n); i++)

int main() {
    pair<ll, ll> A[6];
    rep(i, 6) {
        cin >> A[i].first >> A[i].second;
        if (A[i].first > A[i].second) {
            swap(A[i].first, A[i].second);
        }
    }
    sort(A, A + 6);
    rep(i, 6) if (i & 1) {
        if (A[i].first != A[i - 1].first || A[i].second != A[i - 1].second) {
            return puts("no") & 0;
        }
    }
    vector<pair<ll, ll>> B = {A[0], A[2], A[4]};
    bool flag = 0;
    flag = B[0].first==B[1].first&&B[0].second==B[2].first&&B[1].second==B[2].second;
    cout << (flag ? "yes" : "no") << endl;
}

