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#include <iostream>
#include <vector>

using namespace std;

int longestPath = 0, longestId = 0;
vector < vector <bool> > sasiedziKwadrat;
vector < vector <int> > sasiedziLista;

void DFS(int start, vector <int> path, int leng)
{
    path.push_back(start);
    leng++;
    if(sasiedziLista[start].size() == 0)
    {
        if(leng > longestPath)
        {
            //cout << "x " << endl;
            //for(int i = 0; i < path.size(); i++)
            //{
            //    cout << path[i] << " ";
            //}
            //cout << endl;
            longestPath = leng;
            longestId = path[(leng - 1) / 2];
            //cout << ">> " << longestId << endl;
        }
    }
    else
    {
        for(int i = 0; i < sasiedziLista[start].size(); i++)
        {
            //cout << "-> " << sasiedziLista[start][i] << " " << leng << endl;
            DFS(sasiedziLista[start][i], path, leng);
        }
    }
}

int main()
{
    vector <int> starterzy;
    vector <int> pat;
    int ileUmiejetnosci, ileZaleznosci, ileUsunac, a, b;
    bool isOk;
    cin >> ileUmiejetnosci >> ileZaleznosci >> ileUsunac;
    for(int i = 0; i < ileUmiejetnosci; i++)
    {
        sasiedziKwadrat.push_back(vector <bool>());
        sasiedziLista.push_back(vector <int>());
        for(int j = 0; j < ileUmiejetnosci; j++)
        {
            sasiedziKwadrat[i].push_back(0);
        }
    }
    for(int i = 0; i < ileZaleznosci; i++)
    {
        cin >> a >> b;
        sasiedziKwadrat[a - 1][b - 1] = true;
        sasiedziLista[a - 1].push_back(b - 1);
    }

    for(int z = 0; z < ileUsunac; z++)
    {
        starterzy.clear();
        longestPath = 0;
        for(int i = 0; i < ileUmiejetnosci; i++)
        {
            isOk = true;
            for(int j = 0; j < ileUmiejetnosci; j++)
            {
                if(sasiedziKwadrat[j][i] == true)
                {
                    isOk = false;
                    break;
                }
            }
            if(isOk == true)
            {
                starterzy.push_back(i);
            }
        }
        for(int i = 0; i < starterzy.size(); i++)
        {
            DFS(starterzy[i], pat, 0);
        }
        for(int i = 0; i < sasiedziLista[longestId].size(); i++)
        {
            sasiedziKwadrat[longestId][sasiedziLista[longestId][i]] = false;
        }
        sasiedziLista[longestId].clear();
        for(int i = 0; i < ileUmiejetnosci; i++)
        {
            for(int j = 0; j < sasiedziLista[i].size(); j++)
            {
                if(sasiedziLista[i][j] == longestId)
                {
                    //cout << "<< " << sasiedziLista[i][j] << endl;
                    sasiedziLista[i].erase(sasiedziLista[i].begin() + j);
                    break;
                }
            }
        }
    }
    starterzy.clear();
    longestPath = 0;
    for(int i = 0; i < ileUmiejetnosci; i++)
    {
        isOk = true;
        for(int j = 0; j < ileUmiejetnosci; j++)
        {
            if(sasiedziKwadrat[j][i] == true)
            {
                isOk = false;
                break;
            }
        }
        if(isOk == true)
        {
            starterzy.push_back(i);
        }
    }
    //cout << "there" << endl;
    for(int i = 0; i < starterzy.size(); i++)
    {
        DFS(starterzy[i], pat, 0);
    }
    if(ileUsunac >= ileUmiejetnosci)
    {
        cout << 0 << endl;
    }
    else
    {
        cout << longestPath << endl;
    }

    /*for(int i = 0; i < ileUmiejetnosci; i++)
    {
        cout << i << " > ";
        for(int j = 0; j < ileUmiejetnosci; j++)
        {
            cout << sasiedziKwadrat[i][j] << " ";
        }
        cout << endl;
    }
    cout << endl;
    for(int i = 0; i < ileUmiejetnosci; i++)
    {
        cout << i << " > ";
        for(int j = 0; j < sasiedziLista[i].size(); j++)
        {
            cout << sasiedziLista[i][j] << " ";
        }
        cout << endl;
    }*/
    return 0;
}