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#include <bits/stdc++.h>

using namespace std;

typedef long long int LL;

const int N = 307;
const int MAXPOSSIBLE = 1e6;

int n, m, k;
int ans = N;

bool block[N];
int Length[N];
vector <int> G[N];

int Count(int a, int b){
	LL ret = 1LL;
	while(b--)
		ret *= a;
	
	if(ret > MAXPOSSIBLE)
		return MAXPOSSIBLE + 1;
	return ret;
}

int calc(){
	int ret = 0;
	for(int i = n; i >= 1; --i){
		if(block[i])
			continue;

		Length[i] = 1;
		for(int v: G[i])
			if(!block[v])
				Length[i] = max(Length[i], Length[v] + 1);
		ret = max(ret, Length[i]);
	}
	
	return ret;
}

void go(int Left){
	if(Left == 0){
		ans = min(ans, calc());
		return;
	}
	
	int t = calc();
	int Start = -1;

	for(int i = 1; i <= n; ++i)
		if(!block[i] && Length[i] == t)
			Start = i;
	
	vector <int> maybe;
	maybe.push_back(Start);

	while(Length[Start] > 1){
		for(int v: G[Start])
			if(!block[v] && Length[v] + 1 == Length[Start]){
				Start = v;
				break;
			}
		
		maybe.push_back(Start);
	}
	
	for(int v: maybe){
		block[v] = true;
		go(Left - 1);
		block[v] = false;
	}
}

int main(){
	scanf("%d %d %d", &n, &m, &k);
	for(int i = 0; i < m; ++i){
		int u, v;
		scanf("%d %d", &u, &v);
		G[u].push_back(v);
	}

	if(n <= k){
		puts("0");
		return 0;
	}
	
	if(m <= k){
		puts("1");
		return 0;
	}
	
	go(k);
	printf("%d\n", ans);
	return 0;
}