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#include <algorithm>
#include <cmath>
#include <iostream>
#include <string>
#include <vector>
using namespace std;

typedef long long ll;
typedef unsigned int ui;
typedef pair<int, int> pii;
typedef vector<int> vi;

struct Graph {
	vector<vector<int>> adj_list;
	Graph(int n) : adj_list(n) { }
	void add_edge(int v1, int v2) {
		adj_list[v1].push_back(v2);
	}
	int longest_path(vector<int> ignored);
};

bool contains(vector<int> &vec, int i) {
	for (int x : vec) {
		if (x == i)
			return true;
	}
	return false;
}

int Graph::longest_path(vector<int> ignored) {
	vector<int> distance(adj_list.size(), 1);
	int mx = 0;
	
	for (int i = 0; i < adj_list.size(); ++i) {
		if (contains(ignored, i))
			continue;
		for (int next : adj_list[i]) {
			if (contains(ignored, next))
				continue;
			distance[next] = max(distance[next], distance[i] + 1);
			mx = max(mx, distance[next]);
		}
	}

	//for (int i : distance)
	//	cerr << i << " ";
	//cerr << endl;

	return mx;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);

	int n, m, k, x, y;
	cin >> n >> m >> k;
	Graph g(n);
	for (int i = 0; i < m; ++i) {
		cin >> x >> y;
		g.add_edge(x - 1, y - 1);
	}

	if (k == n)
		cout << 0 << endl;
	else if (k == 0)
		cout << g.longest_path({}) << endl;
	else if (k == 1) {
		int mn = 1000000;
		for (int i = 0; i < n; ++i) {
			mn = min(mn, g.longest_path({i}));
		}
		cout << mn << endl;
	}
	else if (k == 2) {
		int mn = 1000000;
		for (int i = 0; i < n; ++i) {
			for (int j = i + 1; j < n; ++j) {
				mn = min(mn, g.longest_path({i, j}));
			}
		}
		cout << mn << endl;
	}
	else if (k == 3) {
		int mn = 1000000;
		for (int i = 0; i < n; ++i) {
			for (int j = i + 1; j < n; ++j) {
				for (int k = j + 1; k < n; ++k) {
					mn = min(mn, g.longest_path({i, j, k}));
				}
			}
		}
		cout << mn << endl;
	}
	else if (k >= 4) {
		int mn = 1000000;

		for (int i = 0; i < n; ++i) {
			for (int j = i + 1; j < n; ++j) {
				for (int k = j + 1; k < n; ++k) {
					for (int l = k + 1; l < n; ++l) {
						mn = min(mn, g.longest_path({i, j, k, l}));
					}
				}
			}
		}
		cout << mn << endl;
	}
    return 0;
}