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#include<bits/stdc++.h>
using namespace std;
typedef long long int lld;

struct Graph{
	vector<int> path;
	int dist;
	bool lock;

	Graph(void): dist(0), lock(false) {}
};

vector<Graph> g;

void clear(void){
	for(auto& i : g)
		i.dist = 1;
}

int check(void){
	clear();
	int r = 0;

	for(int i=0;i<g.size();i++){
		if(g[i].lock)
			continue;

		r = max(r, g[i].dist);

		for(int u : g[i].path)
			g[u].dist = max(g[u].dist, g[i].dist+1);
	}

	return r;
}

vector<bool> M;
int res;
int tmp;

void gen(int k){
	if(k == 0){
		int v = check();

		if(tmp > v){
			tmp = v;
			for(int i=0;i<M.size();i++)
				M[i] = g[i].lock;
		}

		return;
	}

	for(int i=0;i<g.size();i++)
		if(!g[i].lock){
			g[i].lock = true;
			gen(k-1);
			g[i].lock = false;
		}

	return;
}

void calc(vector<int>& t){
	fill(M.begin(), M.end(), false);
	for(auto& i : g)
		i.lock = false;
	tmp = g.size();

	for(int i : t){
		gen(i);
		for(int j=0;j<g.size();j++)
			g[j].lock = M[j];
	}

	res = min(res, tmp);
}

vector<vector<int> > t[5];

int main(void){
	ios_base::sync_with_stdio(false);

	lld n,m,k;
	cin >> n >> m >> k;

	g.resize(n);
	M.resize(n);
	for(int i=0;i<m;i++){
		int a,b;
		cin >> a >> b;
		a--, b--;

		g[a].path.push_back(b);
	}

	t[1].push_back({1});

	t[2].push_back({2});

	t[3].push_back({1,1,1});
	t[3].push_back({1,2});
	t[3].push_back({2,1});

	t[4].push_back({1,1,1,1});
	t[4].push_back({2,1,1});
	t[4].push_back({1,2,1});
	t[4].push_back({1,1,2});
	t[4].push_back({2,2});

	if(pow(n,k)*n <= 1e8){
		vector<int> t;
		t.push_back(k);
		res = n;
		calc(t);
	}else{
		res = n;
		for(auto& i : t[k])
			calc(i);
	}

	cout << res << "\n";

	return 0;
}