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#include <bits/stdc++.h>

#define F first
#define S second
#define ll long long
#define ld long double
#define vi vector < int >
#define vll vector < ll >
#define pb push_back
#define sz(x) int((x).size())
#define pii pair < int, int >
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define vpii vector < pii >
#define sqr(x) ((x)*(x))
#define fenwick(x) ((x) & -(x))
#define debug(x) cout << "[ " << #x << " ]: " << x << "\n";
#define we ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

using namespace std;

//CZY DANE POSORTOWANE, N = 0, N = 1, CZYTANIE TRESCI, < rosnaco, > malejaco

const int MAX = 320;

vi graf[MAX];
int N, M, K;
bitset <MAX> odw;
int stopnie[MAX];
int kopia[MAX];
int dlugosc[MAX];
void blok(int i)
{
	odw[i] = 1;
	for (auto &p : graf[i])
	{
		stopnie[p]--;
	}
}

void rblok(int i)
{
	odw[i] = 0;
	for (auto &p : graf[i])
	{
		stopnie[p]++;
	}
}

int sprawdz()
{
	queue <int> kolejka;

	for (int i = 1; i <= N; ++i)
	{
		kopia[i] = stopnie[i];
		dlugosc[i] = 0;
		if (!stopnie[i] && !odw[i])
		{
			kolejka.push(i);
		}
	}

	while (!kolejka.empty())
	{
		int u = kolejka.front();

		kolejka.pop();

		for (auto &p : graf[u])
		{
			if (!odw[p])
			{
				--kopia[p];
				dlugosc[p] = max(dlugosc[p], dlugosc[u] + 1);
				if (!kopia[p])
				{
					kolejka.push(p);
				}
			}
		}
	}

	int ans = 0;

	for (int i = 1; i <= N; ++i)
	{
		if (!odw[i])ans = max(ans, dlugosc[i]);
	}

	return ans + 1;
}


void czworka()
{
	int ans = 30000;

	for (int i = 1; i <= N - 3; ++i)
	{
		for (int j = i + 1; j <= N - 2; ++j)
		{
			for (int k = j + 1; k <= N - 1; ++k)
			{
				for (int l = k + 1; l <= N; ++l)
				{
					blok(i);
					blok(j);
					blok(k);
					blok(l);
					ans = min(ans, sprawdz());
					rblok(i);
					rblok(j);
					rblok(k);
					rblok(l);
				}
			}
		}
	}

	cout << ans << "\n";
}

void trojka()
{
	int ans = 30000;

	for (int i = 1; i <= N - 2; ++i)
	{
		for (int j = i + 1; j <= N - 1; ++j)
		{
			for (int k = j + 1; k <= N; ++k)
			{
				blok(i);
				blok(j);
				blok(k);
				ans = min(ans, sprawdz());
				rblok(i);
				rblok(j);
				rblok(k);
			}
		}
	}

	cout << ans << "\n";
}

void dwojka()
{
	int ans = 30000;

	for (int i = 1; i <= N - 1; ++i)
	{
		for (int j = i + 1; j <= N; ++j)
		{
			blok(i);
			blok(j);
			ans = min(ans, sprawdz());
			rblok(i);
			rblok(j);
		}
	}

	cout << ans << "\n";
}

void jedynka()
{
	int ans = 30000;

	for (int i = 1; i <= N; ++i)
	{
		blok(i);
		ans = min(ans, sprawdz());
		rblok(i);
	}

	cout << ans << "\n";
}

int main()
{
	we

	cin >> N >> M >> K;

	if (N == K)return cout << 0 << "\n", 0;

	for (int i = 0; i < M; ++i)
	{
		int a, b;
		cin >> a >> b;
		graf[a].pb(b);
		stopnie[b]++;
	}

	if (K == 1)
	{
		jedynka();
	}
	if (K == 2)
	{
		dwojka();
	}
	if (K == 3)
	{
		trojka();
	}
	if (K == 4)
	{
		czworka();
	}

	return 0;
}