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
#include <iostream>
#include <vector>

using namespace std;

const int MAXN = 305, inf = 1e9;

int res = inf, dp[MAXN], k, n, num = 1, vis[MAXN];
vector<int> G[MAXN];

void dfs(int v) {
    dp[v] = 1, vis[v] = num;
    for (int u : G[v]) {
        if (vis[u] < num) {
            dfs(u);
        }
        dp[v] = max(dp[v], dp[u] + 1);
    }
}

int bads[5];
void rek(int j) {
    if (j > k) {
        num++;
        for (int i = 1; i <= k; i++) {
            vis[bads[i]] = num;
            dp[bads[i]] = 0;
        }

        dfs(0);
        res = min(res, dp[0] - 1);
        return;
    }

    for (int i = bads[j - 1] + 1; i <= n; i++) {
        bads[j] = i;
        rek(j + 1);
    }
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    int m;
    cin >> n >> m >> k;
    for (int i = 0; i < m; i++) {
        int a, b;
        cin >> a >> b;
        G[a].push_back(b);
    }

    for (int i = 1; i <= n; i++) {
        G[0].push_back(i);
    }

    rek(1);

    cout << res << "\n";
}