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//Jan Sosnowski
//runda 2
#include<iostream>
#include<vector>
using namespace std;

int n,m,k;

vector <bool> odw;
vector <int> dlugosc;
vector <int> v;
vector < vector < int > > g; //wejscie
vector < vector < int > > g2; //odwrotnie

void czysc_dlug(){
	for(int i =0;i<=n;i++){
		dlugosc[i] = 1;
	}
}


int max_sciezka(){
	int sciezka = 0;
	for(int i=1;i<=n;i++){
		if(odw[i] == 0){
			sciezka = max(sciezka,dlugosc[i]);
			for(int j =0;j<g[i].size();j++){
				dlugosc[g[i][j]] = max(dlugosc[g[i][j]],dlugosc[i]+1);
			}
		}	
	}
//	cout << " max_sciezka  " << sciezka << "\n";
	return sciezka;	
}


int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	cin >> n >> m >> k;
	v.clear();
	g.clear();
	odw.clear();
	int x,y;
	for(int i =0;i<=n;i++){
		g.push_back(v);
		g2.push_back(v);
		odw.push_back(0);
		dlugosc.push_back(1);
	}
	for(int i =0;i<m;i++){
		cin >> x >> y;
		g[x].push_back(y);
		g2[y].push_back(x);
	}
	int wyn = n;
	
	if(k==n) wyn = 0;
	
	else if(k == n-1) wyn = 1;
	
	else if(k==0){
		wyn = max_sciezka();
	}
	
	else if(k==1){
		for(int i =1;i<=n;i++){
			czysc_dlug();
			odw[i] = 1;
			wyn = min(wyn,max_sciezka());
			odw[i] = 0;
//			cout << wyn << "\n";
		}
	}
	
	else if(k==2){
		for(int i = 1;i<n;i++){
			odw[i] = 1;
			for(int j = i+1;j<=n;j++){
				odw[j] = 1;
				czysc_dlug;
				wyn = min(wyn,max_sciezka());
				odw[j] = 0;
			}
			odw[i] = 0;
		}
	}
	
	else if(k==3){
		for(int i = 1;i<n-1;i++){
			odw[i] = 1;
			for(int j = i+1;j<n;j++){
				odw[j] = 1;
				for(int l = j+1;l<=n;l++){
					odw[l] = 1;
					wyn = min(wyn,max_sciezka());
					odw[l] = 0;
				}
				odw[j] = 0;
			}
			odw[i] = 0;
		}	
	}
	
	else if(k==4){
		for(int i =1;i<n-2;i++){
			odw[i] = 1;
			for(int j=i+1;j<n-1;j++){
				odw[j] = 1;
				for(int l = j+1;l<n;l++){
					odw[l] = 1;
					for(int p=l+1;p<=n;p++){
						odw[p] = 1;
						wyn = max(wyn,max_sciezka());
						odw[p] = 0;
					}
					odw[l] = 0;
				}
				odw[j] = 0;
			}
			odw[i] = 0;
		}
	}
	
	cout << wyn;
}