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
#include <bits/stdc++.h>
using namespace std;
vector <int> blocked;
vector <vector <int> > G;
int n;
int rek(int k){
    vector <int> dp(n+1, 0);
    vector <int> path(n+1, 0);
    vector <int> pat;
    for(int i = 1; i <= n; ++i){
        if(blocked[i])continue;
        for(int j : G[i]){
            if(blocked[j])continue;
            if(dp[j] + 1 > dp[i]){
                path[i] = j;
            }
            dp[i] = max(dp[j] + 1, dp[i]);
        }
    }
    int x = 0;
    for(int i = 1; i <= n; ++i)x = max(dp[i], x);
    if(k > 0){
        for(int i = 1; i <= n; ++i)if(dp[i] == x){
            int u = i;
            pat.push_back(u);
            while(u != 0){
                u = path[u];
                pat.push_back(u);
            }
            break;
        }
        int t = 1e9;
        for(int g : pat){
            blocked[g] = 1;
            t = min(t, rek(k-1));
            blocked[g] = 0;
        }
        return t;
    }
    return x;
}

int main(){
    ios_base::sync_with_stdio(0);
    cin >> n;
    int m;
    cin >> m;
    int k;
    cin >> k;
    if(k >= n){
        cout << 0 << '\n';
        return 0;
    }
    G.resize(n+1);
    for(int i = 0; i < m; ++i){
        int a, b;
        cin >> a >> b;
        G[b].push_back(a);
    }
    blocked.resize(n+1,0);
    cout << rek(k) + 1 << '\n';
}