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#include <bits/stdc++.h>
using namespace std;

struct Graph { 
	int n;
	vector<int> pre;
	vector<vector<int> > suc;
	vector<int> erased;
	vector<int> unerasable;

	void init(int nn) {
		n = nn;
		pre.resize(n, 0);
		suc.resize(n);
		erased.resize(n, 0);
		unerasable.resize(n, 0);
	}

	void addEdge(int a, int b) {
		for (int i=0; i<suc[a].size(); ++i) if (suc[a][i] == b) return;
		suc[a].push_back(b);
		++pre[b];
	}

	void eraseVertex(int a) {
		erased[a] = 1;
		for (int i=0; i<suc[a].size(); ++i)
			--pre[suc[a][i]];
	}

	void restoreVertex(int a) {
		erased[a] = 0;
		for (int i=0; i<suc[a].size(); ++i)
			++pre[suc[a][i]];
	}

	int diag(vector<int> &path, bool buildPath = true) {
		vector<int> cnt(pre);
		queue<int> q;
		for (int i=0; i<n; ++i) if (cnt[i] == 0 && erased[i] == 0) q.push(i);
		vector<int> dist(n, 1);
		vector<int> prev(n, -1);
		int res = 0;
		int last = 0;
		while (!q.empty()) {
			int x = q.front(); q.pop();
			if (dist[x] > res) {
				res = dist[x];
				last = x;
			}
			for (int k=0; k<suc[x].size(); ++k) {
				int y = suc[x][k];
				if (erased[y]) continue;
				if (dist[x] + 1 > dist[y]) {
					dist[y] = dist[x] + 1;
					prev[y] = x;
				}
				--cnt[y];
				if (cnt[y] == 0)
					q.push(y);
			}
		}

		if (buildPath) {
			while (last >= 0) {
				path.push_back(last);
				last = prev[last];
			}
		}

		return res;
	}
};

Graph g;

int solve(int k) {
	vector<int> path;
	if (k == 0) return g.diag(path, false);

	g.diag(path);
	int res = 1000;
	int cur;
	int i = path.size() / 2;
	int j = i + 1;
	int x;
	for (; i>=0 || j<path.size(); --i, ++j) {
		if (i >= 0) {
			x = path[i];
			++g.unerasable[x];
			if (g.unerasable[x] == 1) {
				g.eraseVertex(x);
				cur = solve(k-1);
				if (cur < res)
					res = cur;
				g.restoreVertex(x);
			}
		}
		if (j < path.size()) {
			x = path[j];
			++g.unerasable[x];
			if (g.unerasable[x] == 1) {
				g.eraseVertex(x);
				cur = solve(k-1);
				if (cur < res)
					res = cur;
				g.restoreVertex(x);
			}
		}
	}
	for (int i=0; i<path.size(); ++i)
		--g.unerasable[path[i]];
	return res;
}

int read() { int n; scanf("%d", &n); return n; }



int mainSolve() {
	int n = read();
	int m = read();
	int k = read();

	if (k >= n) return 0;

	g.init(n);

	for (int i=0; i<m; ++i) {
		int a = read() - 1;
		int b = read() - 1;
		g.addEdge(a, b);
	}

	int res = solve(k);
	return res;
}




int main() {
	int res = mainSolve();
	printf("%d\n", res);

	return 0;
}