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
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
/*{{{*/
#include <bits/stdc++.h>
#ifdef LOCAL
int c_;
#define cout (c_?cerr:cout)
#define debug(...) {cerr<<(c_?"":"\033[96;1m");\
++c_;__VA_ARGS__;--c_;cerr<<(c_?"":"\033[0m");}
#else
#define debug(...) {}
#endif
#define st first
#define nd second
#define all(...) begin(__VA_ARGS__), end(__VA_ARGS__)
#define dump(...) debug(print(#__VA_ARGS__" =", __VA_ARGS__))
#define dump_range(...) debug(cerr<<#__VA_ARGS__": ";print_range(__VA_ARGS__);)
using namespace std;
template< typename t >
using V = vector< t >;
using ll = long long;
using ld = long double;
void print(){cout<<'\n';}
template< typename t, typename... v >
void print(const t& a, const v&... b)
{cout<<a<<(sizeof...(b)?" ":"");print(b...);}
template< typename t >
void print_range(t a, const t& b)
{while (a!=b) cout<<(*a++)<<' ';cout<<'\n';}
/*}}}*/

using ull = unsigned long long;

constexpr int nax = 300, op = 3e8;

int n, m, k, res, st;
ull dp[nax + 1];
ull dp2[nax + 1];
int rs[nax + 1];
V< int > gr[nax + 1];
V< int > rg[nax + 1];
pair< ull, int > ilo[nax + 1];
bool lk[nax + 1], bl[nax + 1];

void resuj()
{
    for (int i = 1; i <= n; ++i)
        rs[i] = (not bl[i]);

    for (int i = n; i >= 1; --i)
        if (not bl[i])
            for (int s : gr[i])
                if (not bl[s])
                    rs[i] = max(rs[i], rs[s] + 1);

    int r = *max_element(rs + 1, rs + n + 1);
    res = min(r, res);
}

void heuruj()
{
    for (int i = 1; i <= n; ++i)
            dp[i] = dp2[i] = not bl[i];

    for (int i = n; i >= 1; --i)
        if (not bl[i])
            for (int s : gr[i])
                if (not bl[s])
                    dp[i] += dp[s] + 1;

    for (int i = 1; i <= n; ++i)
        if (not bl[i])
            for (int s : rg[i])
                if (not bl[s])
                    dp2[i] += dp2[s] + 1;

    for (int i = 1; i <= n; ++i)
        if (not lk[i])
            ilo[i] = {dp[i] * dp2[i], i};
        else
            ilo[i] = {0, i};

}

void heura(int il)
{
    if (il == k)
    {
        resuj(); 
        //for (int i = 1; i <= n; ++i)
            //if (bl[i])
                //cout << i << ' ';
        //cout << '\n';
        
        return;
    }

    heuruj();

    sort(ilo + 1, ilo + n + 1);

    V< int > kand;

    for (int i = n; i >= max(n - st + 1, 0); --i)
        if (not lk[ilo[i].nd])
            kand.push_back(ilo[i].nd);

    for (int v : kand)
    {
        lk[v] = bl[v] = true;
        heura(il + 1);
        bl[v] = false;
    }

    for (int v : kand)
        lk[v] = false;
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    cin >> n >> m >> k;

    res = n;

    st = op / (n + m);
    if (k >= 3)
        st = sqrt(sqrt(st));
    else if (k == 2)
        st = sqrt(st);

    cerr << st << '\n';

    
    for (int i = 0; i < m; ++i)
    {
        int p, q; cin >> p >> q;
        gr[p].push_back(q);
        rg[q].push_back(p);
    }

    heura(0);

    print(res);
}