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#include <cstdio>
#include <cstring>
#include <vector>
#include <cstdlib>
#include <set>
#include <algorithm>

using namespace std;

vector<int> edges[309];
int mx = 0;
int cnt = 0;
int n, m, k;

vector<vector<int>> paths;

void dfs(int index, int depth, vector<int>& path) {
	path.push_back(index);
	if (depth == 0) {
		paths.push_back(path);
	}
	else {
		for (auto e: edges[index]) {
			dfs(e, depth-1, path);
		}
	}
	path.pop_back();
}

static char taken[309];
bool backtrack(int remaining, size_t path_index) {
	if (path_index == paths.size()) {
		return true;
	}
	bool any = false;
	for (auto p: paths[path_index]) {
		if (taken[p]) {
			any = true;
			break;
		}
	}
	if (any) {
		return backtrack(remaining, path_index+1);
	}
	if (remaining == 0) return false;
	for (auto p: paths[path_index]) {
		taken[p] = true;
		bool r = backtrack(remaining - 1, path_index + 1);
		taken[p] = false;
		if (r) return true;
	}
	return false;
}

bool forbidden[309];
int dp[309];
int brucheck() {
	for (int i=0; i<n; i++) {
		dp[i] = 1;
	}
	int mx = 0;
	for (int i=0; i<n; i++) {
		if (forbidden[i]) continue;
		if (dp[i] > mx) mx = dp[i];
		for (auto e: edges[i]) {
			if (forbidden[e]) continue;
			if (dp[i] + 1 > dp[e]) dp[e] = dp[i] + 1;
		}
	}
	/*
	printf("Brucheck (");
	for (int i=0; i<n; i++) {
		if (forbidden[i])
			printf("%d, ", i+1);
	}
	printf(") -> %d\n", mx);
	for (int i = 0; i < n; i++) {
		printf("%d ", dp[i]);
	}
	printf("\n");
	*/
	return mx;
}

int main() {
	scanf("%d %d %d", &n, &m, &k);
	vector<pair<int, int>> ed;
	for (int i=0; i<m; i++) {
		int x, y;
		scanf("%d %d", &x, &y);
		x--; y--;
		edges[x].push_back(y);
		ed.push_back({x, y});
	}
	if (n < 75) {
		int mx = 1e9;
			mx = min(mx, brucheck());
		if (k > 0)
		for (int i0 = 0; i0 < n; i0++) {
			forbidden[i0] = true;
			mx = min(mx, brucheck());
		if (k > 1)
		for (int i1 = i0+1; i1 < n; i1++) {
			forbidden[i1] = true;
			mx = min(mx, brucheck());
		if (k > 2)
		for (int i2 = i1+1; i2 < n; i2++) {
			forbidden[i2] = true;
			mx = min(mx, brucheck());
		if (k > 3)
		for (int i3 = i2+1; i3 < n; i3++) {
			forbidden[i3] = true;
			mx = min(mx, brucheck());
			forbidden[i3] = false;
		}
			forbidden[i2] = false;
		}
			forbidden[i1] = false;
		}
			forbidden[i0] = false;
		}
		printf("%d\n", mx);
		return 0;
	}

	for (int check = 1; ; check++) {
		paths.clear();
		for (int i=0; i<n; i++) {
			vector<int> v;
			dfs(i, check, v);
		}
		set<vector<int>> comp(paths.begin(), paths.end());
		paths = vector<vector<int>> (comp.begin(), comp.end());
		sort(paths.begin(), paths.end(), [](vector<int>a, vector<int>b){
			   	return a.size() < b.size(); });
		bool res = backtrack(k, 0);
		if (res) {
			printf("%d\n", check);
			break;
		}
	}
}