1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
#include <bits/stdc++.h>
using namespace std;

#define pb push_back
const int ac = 1e3;
int n, m, k; 

vector<vector<int> > I;
int D[ac];
int O[ac];
int X[4];
int W[ac];

int solve()
{
	int m = 0;
	for (int i = n - 1; i >= 0; i--)
	{
		bool b = 0;
		for (int j = 0; j < k; j++) if (X[j] == O[i]) { b = 1; break; }
		if (b) { W[O[i]] = 0; continue; }
		W[O[i]] = 1;
		for (int j = 0; j < I[O[i]].size(); j++)
			W[O[i]] = max(W[O[i]], W[I[O[i]][j]] + 1);
		m = max(m, W[O[i]]);
	}
	return m;
}

int gen(int c = 0, int b = 0)
{
	if (c == k) return solve();
	int w = 1e9;
	for (int i = b; i < n; i++)
		X[c] = i, w = min(w, gen(c + 1, i + 1));
	return w;
}

int main()
{
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cin >> n >> m >> k;
	I.resize(n);
	for (int i = 0; i < m; i++)
	{
		int a, b; cin >> a >> b; a--; b--;
		I[a].pb(b);
		D[b]++;
	}
	vector<int> Q;
	for (int i = 0; i < n; i++)
		if (!D[i]) Q.pb(i);
	int j = 0;
	while (j < Q.size())
	{
		O[j] = Q[j];
		for (int i = 0; i < I[Q[j]].size(); i++)
		{
			D[I[Q[j]][i]]--;
			if (!D[I[Q[j]][i]])
				Q.pb(I[Q[j]][i]);
		}
		j++;
	}
	cout << gen() << '\n';
}