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#include <iostream>
#include <algorithm>
#include <vector>

using namespace std;

struct v {
    vector<int> L;
    int deg_in = 0;
    int depth = -1;
    int printed_out = 0;
    int dead = 0;
};

void dfs(vector<v> &G, int k) {
    //cout<<k<<endl;
    if(G[k].dead)
        return;
    for (auto x: G[k].L) {
        if (G[x].dead)
            continue;
        if (G[x].depth == -1) {
            dfs(G, x);
        }
        G[k].depth = max(G[x].depth + 1, G[k].depth);
        //cout << k <<   G[k].depth << "<"<< endl;
    }
    if (G[k].depth == -1)
        G[k].depth = 1;
}

void print_longest_paths(vector<v> &G, int k, vector<int> &Out) {
    if (G[k].printed_out)
        return;
    G[k].printed_out = 1;
    for (auto x: G[k].L) {
        if (G[x].depth == G[k].depth - 1) {
            print_longest_paths(G, x, Out);
            break;
        }
    }
    Out.push_back(k);
}

int GetLongest(vector<v> &G, vector<int> &ToKill) {
    for (auto x: ToKill) {
//        cout<<":"<<x<<" :)"<<endl;
        G[x].dead = 1;
        for (auto son: G[x].L)
            G[son].deg_in--;
    }
    for (auto &x: G) {
        x.depth = -1;
        x.printed_out = 0;
    }


    int biggest = 0;

    for(int i = 0;i < G.size();i++) {
        if (G[i].dead)
            continue;
        dfs(G, i);
    }
    for (auto x: G) {
        biggest = max(x.depth, biggest);
    }
    //cout << biggest<<endl;

    for (auto x: ToKill) {
        G[x].dead = 0;
        for (auto son: G[x].L)
            G[son].deg_in++;
    }
    //cout << V.back().first << endl;
//    cout << biggest <<" !! ";
    return biggest;
}

int main()
{
    int n, m, k;
    cin >> n >> m >> k;
    vector <v> G(n);
    for (int i = 0;i < m;i++) {
        int a,b;
        cin>>a>>b;
        a--;b--;
        if(a > b)
            swap(a, b);
        G[a].L.push_back(b);
        G[b].deg_in++;
    }

    vector<pair<int, vector<int> > > V;



    for(int i = 0;i < G.size();i++) {
        dfs(G, i);
    }

    if(k == 0) {
        int best = 0;
        for(int i = 0;i < G.size();i++) {
            best = max(G[i].depth, best);
        }
        cout << best << endl;
        return 0;
    }

    vector<pair<int, int> > Firsts;
    for (int i = 0;i < G.size();i++) {
        Firsts.push_back({G[i].depth, i});
    }
    sort(Firsts.begin(), Firsts.end());

    for (auto x = Firsts.rbegin(); x != Firsts.rend();x++) {
        int i = x->second;
        //cout << x->first << endl;
        if(G[i].deg_in == 0) {
            vector<int> Out;
            print_longest_paths(G, i, Out);
            V.push_back({Out.size(), Out});
        }
    }
    sort(V.begin(), V.end());
//    for (auto x = V.begin(); x != V.end();x++)
//        cout << x->first << endl;

    vector<int> CandidatesToDelete;
    int i = 0;
    for (auto x = V.rbegin(); x != V.rend();x++) {
        if (i++ == k)
            break;
        for (auto y: x->second)
            CandidatesToDelete.push_back(y);
    }
//    cout<<CandidatesToDelete.size() << endl;
//    for (auto x: CandidatesToDelete)
//        cout<<x<<"!"<<endl;
    //return 0;
    int best = 9999999;

    for(int i = 0;i < CandidatesToDelete.size();i++) {
        vector<int> ToKill = {CandidatesToDelete[i]};
        if(k == 1) {
            best = min(best, GetLongest(G, ToKill));
            ToKill.pop_back();
            continue;
        }
        for (int j = i + 1;j < CandidatesToDelete.size();j++) {
            ToKill.push_back(CandidatesToDelete[j]);
            if(k == 2) {
                best = min(best, GetLongest(G, ToKill));
                ToKill.pop_back();
                continue;
            }
            for (int l = j + 1;l < CandidatesToDelete.size();l++) {
                ToKill.push_back(CandidatesToDelete[l]);
                if(k == 3) {
                    best = min(best, GetLongest(G, ToKill));
                    ToKill.pop_back();
                    continue;
                }
                for (int d = l + 1;d < CandidatesToDelete.size();d++) {
                    ToKill.push_back(CandidatesToDelete[d]);
                    if(k == 4) {
                        best = min(best, GetLongest(G, ToKill));
                        ToKill.pop_back();
                        continue;
                    }
                }
                ToKill.pop_back();

            }
            ToKill.pop_back();

        }
    }
    cout << best << endl;

    return 0;
}