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#include <bits/stdc++.h>

using namespace std;

const int N = 305;

vector <int> G[N];
int odl[N];
int n, m, k;

void zer(){
    for(int i = 0; i < N; i++){
        odl[i] = -2;
    }
}

void DFS(int v, int o){
    int ma = -1;
    for(int i = 0; i < G[v].size(); i++){
        
        if(G[v][i] != o){
            if(odl[G[v][i]] == -1) continue;
            if(odl[G[v][i]] == -2)DFS(G[v][i], v);
            ma = max(odl[G[v][i]], ma);
        }
    }
    odl[v] = ma + 1;
}

int glob = 1e9;

void start(){
    for(int i = 1; i < n; i++){
        if(odl[i] == -2){
            DFS(i, i);
        }
    }

    int curr = 0;
    for(int i = 1; i < n; i++){
        curr = max(curr, odl[i]);
    }

    glob = min(glob, curr);
}

int main(){
    ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
    cin >> n >> m >> k;
    for(int i = 0; i < m; i++){
        int a, b;
        cin >> a >> b;
        G[a].push_back(b);
    }


    for(int i = 1; i <= n; i++){
        zer();
        odl[i] = -1;
        if(k == 1){
            
            start();
            //cout << "USUWAM " << i << " " << glob << "\n";
        } else 
        for(int j = i + 1; j <= n; j++){
            zer();
            odl[i] = -1;
            odl[j] = -1;
            if(k == 2){
                start();
            } else 
            for(int l = j + 1; l <= n; l++){
                zer();
                odl[i] = -1;
                odl[j] = -1;
                odl[l] = -1;
                if(k == 3){
                    start();
                } else 
                for(int x = l + 1; x <= n; x++){
                    zer();
                    odl[i] = -1;
                    odl[j] = -1;
                    odl[l] = -1;
                    odl[x] = -1;
                    start();
                }
            }
        }
    }

    if(glob == 0)cout << "0\n";
    else cout << glob + 1<< "\n";
}