#include <bits/stdc++.h>

using namespace std;

// ifstream in("test.in");
// ofstream out("test.out");


struct Domino {
    int side1;
    int side2;
};


// Global variables
int n;
int max_length = 1;
unordered_set<Domino*> used_dominos;
vector<Domino*> dominos_by_side[7]; 


// Recursive solution
void buildTrain(int next_side, int current_length) {
    // cout << "Building train; Current length: " << current_length << "; next side: " << next_side << endl;
    if (current_length > max_length) {
        max_length = current_length;

        // Debug print
        // cout << "updated to " << current_length << endl;
        // if (max_length == 8) {
        //     cout << "found 8" << endl;
        //     for (auto it = used_dominos.begin(); it != used_dominos.end(); it++) {
        //         cout << (*it)->side1 << " " << (*it)->side2 << endl;
        //     }
        // }
    }
    
    int stop = dominos_by_side[next_side].size();
    
    for (int i = 0; i < stop; i++) {
        // Looking at Domino dominos_by_side[next_side][i]
        #define matched_domino dominos_by_side[next_side][i]
        // Skip if already part of the train
        if (used_dominos.count(matched_domino) > 0) {
            continue;
        }


        // The logic for elongating the train
        used_dominos.insert(matched_domino);

        // Figure out if the domino matched by side1 or side2:
        int other_side;
        if ((matched_domino->side1) == next_side) {
            other_side = matched_domino->side2;
        } else {
            other_side = matched_domino->side1;
        }

        // The recursion
        buildTrain(other_side, current_length + 1);


        // Deconstruct
        used_dominos.erase(matched_domino);
    }
}


int main(int argc, char *argv[]) {

    string inName = "test.in";
    string outName = "test.out";

    if (argc > 1) {
        inName = argv[1];
        cout << "Using \"" << inName << "\" for test name" << endl;
    } else {
        cout << "Warning: no in name provided, defaulting to test.in" << endl;
    }

    if (argc > 2) {
        outName = argv[2];
        cout << "Using \"" << outName << "\" for out name" << endl;
    } else {
        cout << "Warning: no out name proviced, defaulting to test.out" << endl;
    }

    ifstream in(inName);
    ofstream out(outName);

    in >> n;

    // cout << "n: " << n << endl;

    if (n < 2) {
        out << "1";
        in.close();
        out.close();
        return 0;
    }
    

    Domino* dominos[n];
    for (int i = 0; i < n; i++) {
        Domino* domino = new Domino();
        in >> (*domino).side1;
        in >> (*domino).side2;

        dominos[i] = domino;

        dominos_by_side[(domino -> side1)].push_back(domino);
        dominos_by_side[(domino -> side2)].push_back(domino);
    }

    // Debug print
    for (int j = 0; j < n; j++) {
        cout << dominos[j] << endl;
        cout << (dominos[j]->side1) << " " << (dominos[j]->side2) << endl;
    } 

    used_dominos.clear();
    // for (int i = 0; i < n; i++) {
    //     #define start_domino dominos[i]

    //     // cout << "starting with domino " << start_domino->side1 << " " << start_domino->side2 <<  "" << start_domino << endl;
    //     used_dominos.insert(start_domino);

    //     buildTrain(start_domino->side1, 1);
    //     buildTrain(start_domino->side2, 1);

    //     used_dominos.clear();
    // }

    used_dominos.insert(dominos[2]);
    cout << "start " << dominos[2]->side1 << " " << dominos[2]->side2 << endl;
    buildTrain(dominos[2]->side1, 1); 


    cout << "Result: " << max_length << endl;

    return 0;
}