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#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
using namespace std;

vector < int > G[301], P[301];
bool used[301];

void dfs( vector < int > &st, vector < vector < int > > &V, int x )
{
    int tmp = st[x]-1;

    if ( st[x] == 0 ) return;
    V[st[x]].push_back( x );
    st[x] = 0;

    for ( int i = 0; i < P[x].size(); ++i )
    {
        if ( st[P[x][i]] == tmp ) dfs( st, V, P[x][i] );
    }
}

int fun( int n, int m, int k )
{
    int result = 0, tmp, maks = 0;
    vector < int > st( n+1, 1 );
    vector < vector < int > > V;

    for ( int i = 1; i <= n; ++i )
    {
        if ( used[i] )
        {
            st[i] = 0;
            continue;
        }
        for ( int j = 0; j < P[i].size(); ++j )
        {
            tmp = P[i][j];
            st[i] = max( st[i], st[tmp]+1 );
        }
        maks = max( maks, st[i]);
    }

    if ( maks == n && m == n-1 )
    {
        return ( n - k ) / ( k+1 ) + (bool)(( n - k ) % ( k+1 ));
    }

    if ( k == 0 ) return maks;

    result = maks;
    V.resize( maks+1 );
    for ( int i = 1; i <= n; ++i )
    {
        if ( st[i] == maks )
        {
            dfs( st, V, i );
        }
    }

    for ( int i = 1; i <= maks; ++i )
    {
        if ( V[i].size() <= k )
        {
            for ( int j = 0; j < V[i].size(); ++j )
                used[V[i][j]] = true;

            result = min( result, fun( n, m, k - V[i].size() ) );

            for ( int j = 0; j < V[i].size(); ++j )
                used[V[i][j]] = false;
        }
    }

    return result;
}

int main()
{
    int n, m, k, a, b;
    scanf( "%d%d%d", &n, &m, &k );

    for ( int i = 0; i < m; ++i )
    {
        scanf( "%d%d", &a, &b );
        G[a].push_back( b );
        P[b].push_back( a );
    }
    if ( n <= k )
    {
        printf( "0\n" );
        return 0;
    }

    printf( "%d\n", fun( n, m, k ) );
}