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#include<bits/stdc++.h>
#define mp make_pair
#define pb push_back
#define st first
#define nd second
#define N 304
using namespace std;

int n, m, k;
int ans[N], res = 1e9;
vector<int> G[N], S[5];
bool vis[N], block[N];

void DFS(int v) {
	vis[v] = true;
	for(auto u : G[v]) {
		if(!vis[u] && !block[u])
			DFS(u);
		if(!block[u])
			ans[v] = max(ans[v], ans[u] + 1);
	}
}

pair<int,int> findBest() {
	pair<int,int> best = mp(0,-1);
	for(int i = 1 ; i <= n ; ++i) {
		if(!vis[i] && !block[i])
			DFS(i);
		if(best.nd < ans[i]) {
			best.nd = ans[i];
			best.st = i;
		}
	}
	return best;
}

void checkAns() {
	fill(vis, vis + n + 1, false);
	fill(ans, ans + n + 1, 0);
	pair<int,int> best = findBest();
	res = min(res, best.nd);
}

void search(int l) {
	fill(vis, vis + n + 1, false);
	fill(ans, ans + n + 1, 0);
	pair<int,int> best = findBest();
	S[l].clear();
	while(best.nd > 0) {
		S[l].pb(best.st);
		for(auto u : G[best.st]) {
			if(ans[u] == best.nd - 1 && !block[u]) {
				best.st = u;
				best.nd = ans[u];
				break;
			}
		}
	}
	S[l].pb(best.st);
}

void backTrack(int l) {
	if(l > k) {
		checkAns();
		return;
	}
	search(l);
	for(auto v : S[l]) {
		if(block[v] == true) continue;
		block[v] = true;
		backTrack(l + 1);
		block[v] = false;
	}
}

void init() {
	scanf("%d%d%d", &n, &m, &k);
	for(int i = 0 ; i < m ; ++i) {
		int a, b;
		scanf("%d%d", &a, &b);
		G[a].pb(b);
	}
}

int main() {
	init();
	backTrack(1);
	if(res)
		printf("%d\n", res+1);
	else puts("0");
}