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#pragma GCC optimize ("unroll-loops")
#include <bits/stdc++.h>

#define mp make_pair
#define fi first
#define se second
#define pb push_back
#define all(x) (x).begin(),(x).end()

using namespace std;

typedef long long LL;
typedef pair<int,int> PII;
typedef vector < int > VI;
typedef double D;

const int MN = 100005, inf = 1000000005, mod = 1000000007;
const LL INF = 1000000000000000005LL;

int n, m;

int ile[MN], wyw[MN], per[MN];
VI G[MN];

inline int licz()
{
	int ret = 0;
	for(int i = 1; i <= n; ++i)
	{
		ile[i] = 0;
		if(wyw[i])
			continue;
		for(auto v : G[i])
			ile[i] = max(ile[i], ile[v]);
		++ile[i];
		ret = max(ret, ile[i]);
	}
	return ret;
}

int solve1()
{
	int ans = inf;
	for(int i = 1; i <= n; ++i)
	{
		wyw[i] = 1;
		ans = min(ans, licz());
		wyw[i] = 0;
	}
	return ans;
}

int solve2()
{
	int ans = inf;
	for(int i = 1; i <= n; ++i)
	{
		wyw[i] = 1;
		for(int j = i + 1; j <= n; ++j)
		{
			wyw[j] = 1;
			ans = min(ans, licz());
			wyw[j] = 0;
		}
		wyw[i] = 0;
	}
	return ans;
}

int solve3()
{
	int ans = inf;
	for(int i = 1; i <= n; ++i)
	{
		wyw[per[i]] = 1;
		for(int j = i + 1; j <= n; ++j)
		{
			wyw[per[j]] = 1;
			for(int k = j + 1; k <= n; ++k)
			{
				wyw[per[k]] = 1;
				ans = min(ans, licz());
				wyw[per[k]] = 0;
			}
			if(clock() > 1.9 * CLOCKS_PER_SEC)
				return ans;
			wyw[per[j]] = 0;
		}
		wyw[per[i]] = 0;
	}
	return ans;
}

int solve4()
{
	int ans = inf;
	for(int i = 1; i <= n; ++i)
	{
		wyw[per[i]] = 1;
		for(int j = i + 1; j <= n; ++j)
		{
			wyw[per[j]] = 1;
			for(int k = j + 1; k <= n; ++k)
			{
				wyw[per[k]] = 1;
				for(int l = k + 1; l <= n; ++l)
				{
					wyw[per[l]] = 1;
					ans = min(ans, licz());
					wyw[per[l]] = 0;
				}
				wyw[per[k]] = 0;
			}
			if(clock() > 1.9 * CLOCKS_PER_SEC)
				return ans;
			wyw[per[j]] = 0;
		}
		wyw[per[i]] = 0;
	}
	return ans;
}

int main()
{
	int *a = new int;
	srand((LL)a);
	int k;
	scanf("%d%d%d", &n, &m, &k);
	for(int i = 1; i <= m; ++i)
	{
		int a, b;
		scanf("%d%d", &a, &b);
		G[b].pb(a);
	}
	for(int i = 1; i <= n; ++i)
		per[i] = i;
	random_shuffle(per + 1, per + 1 + n);
	int ans = inf;
	if(k >= n)
	{
		printf("0");
		return 0;
	}
	if(k == 0)
		ans = licz();
	if(k == 1)
		ans = solve1();
	if(k == 2)
		ans = solve2();
	if(k == 3)
		ans = solve3();
	if(k == 4)
		ans = solve4();
	printf("%d", ans);	
}