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#include <iostream>
#include <vector>
using namespace std;
void DFS (vector < vector <int> > &g,vector < int > &deq,  vector <int> &odp,  int s)
{

    int wyn=odp[s]+1;
    for (int i=0;i<g[s].size();++i)
    {
        int x=g[s][i];
        if (odp[x]<wyn)
            odp[x]=wyn;
        --deq[x];
        if (deq[x]==0)
            DFS(g,deq,odp,x);
    }
}
int n,m,k,a,b,wynik,ww;
int main()
{
    cin>>n >> m >> k;
    vector < vector <int> > g (n+1);
    vector < int > stop_w (n+1);
    for (int i=0;i<m;++i)
    {
        cin >> a >> b;
        g[a].push_back(b);
        stop_w[b]++;
    }

    vector <int> odp (n+1,1);
    if (k==0)
    {
        for (int i=1;i<=n;++i)
            if (stop_w[i]==0)
                DFS(g,stop_w,odp,i);
        wynik=0;
        for (int i=1;i<=n;++i)
            if (odp[i]>wynik)
                wynik=odp[i];
        cout << wynik;
        return 0;
    }
    if (k==1)
    {
        vector <int> s=stop_w;
        wynik=1000;
        for (int v=1;v<=n;++v)
        {
            s[v]=-1;
            for (int i=0;i<g[v].size();++i)
                s[g[v][i]]--;
            vector <int> _s=s;
            ww=0;
            for (int i=1;i<=n;++i)
                odp[i]=1;
            for (int j=1;j<=n;++j)
                if (s[j]==0)
                    DFS(g,_s,odp,j);
            for (int i=1;i<=n;++i)
                if (s[i]!=-1&&odp[i]>ww)
                    ww=odp[i];
            if (ww<wynik)
                wynik=ww;
            s[v]=stop_w[v];
            for (int i=0;i<g[v].size();++i)
                s[g[v][i]]++;
        }
        cout << wynik;
        return 0;
    }
    if (k==2)
    {
        vector <int> s=stop_w;
        wynik=1000;
        for (int v=1;v<=n;++v)
        {
            s[v]=-1;
            for (int i=0;i<g[v].size();++i)
                s[g[v][i]]--;
            for (int p=v+1;p<=n;++p)
            {
                s[p]=-1;
                for (int i=0;i<g[p].size();++i)
                    s[g[p][i]]--;
                vector <int> _s=s;
                ww=0;
                for (int i=1;i<=n;++i)
                odp[i]=1;
                for (int j=1;j<=n;++j)
                if (s[j]==0)
                    DFS(g,_s,odp,j);
            for (int i=1;i<=n;++i)
                if (s[i]!=-1&&odp[i]>ww)
                    ww=odp[i];
                if (ww<wynik)
                    wynik=ww;
                s[p]=stop_w[p];
                for (int i=0;i<g[p].size();++i)
                    s[g[p][i]]++;
            }
            s[v]=stop_w[v];
            for (int i=0;i<g[v].size();++i)
                s[g[v][i]]++;
        }
        cout << wynik;
        return 0;
    }
    if (k==3)
    {
        vector <int> s=stop_w;
        wynik=1000;
        for (int v=1;v<=n;++v)
        {
            s[v]=-1;
            for (int i=0;i<g[v].size();++i)
                s[g[v][i]]--;
            for (int q=v+1;q<=n;++q)
            {
            s[q]=-1;
            for (int i=0;i<g[q].size();++i)
                    s[g[q][i]]--;
            for (int p=q+1;p<=n;++p)
            {
                s[p]=-1;
                for (int i=0;i<g[p].size();++i)
                    s[g[p][i]]--;
                vector <int> _s=s;
                ww=0;
                for (int i=1;i<=n;++i)
                odp[i]=1;
                for (int j=1;j<=n;++j)
                    if (s[j]==0)
                        DFS(g,_s,odp,j);
                for (int i=1;i<=n;++i)
                    if (s[i]!=-1&&odp[i]>ww)
                        ww=odp[i];
                if (ww<wynik)
                    wynik=ww;
                s[p]=stop_w[p];
                for (int i=0;i<g[p].size();++i)
                    s[g[p][i]]++;
            }
            s[q]=stop_w[q];
            for (int i=0;i<g[q].size();++i)
                    s[g[q][i]]++;
            }
            s[v]=stop_w[v];
            for (int i=0;i<g[v].size();++i)
                s[g[v][i]]++;
        }
        cout << wynik;
        return 0;
    }
    vector <int> s=stop_w;
        wynik=1000;
        for (int v=1;v<=n;++v)
        {
            s[v]=-1;
            for (int i=0;i<g[v].size();++i)
                s[g[v][i]]--;
            for (int d=v+1;d<=n;++d)
            {
            s[d]=-1;
            for (int i=0;i<g[d].size();++i)
                    s[g[d][i]]--;
            for (int q=d+1;q<=n;++q)
            {
            s[q]=-1;
            for (int i=0;i<g[q].size();++i)
                    s[g[q][i]]--;
            for (int p=q+1;p<=n;++p)
            {
                s[p]=-1;
                for (int i=0;i<g[p].size();++i)
                    s[g[p][i]]--;
                vector <int> _s=s;
                ww=0;
                for (int i=1;i<=n;++i)
                odp[i]=1;
                for (int j=1;j<=n;++j)
                    if (s[j]==0)
                        DFS(g,_s,odp,j);
                for (int i=1;i<=n;++i)
                    if (s[i]!=-1&&odp[i]>ww)
                        ww=odp[i];
                    if (ww<wynik)
                    wynik=ww;
                s[p]=stop_w[p];
                for (int i=0;i<g[p].size();++i)
                    s[g[p][i]]++;
            }
            s[q]=stop_w[q];
            for (int i=0;i<g[q].size();++i)
                    s[g[q][i]]++;
            }
            s[d]=stop_w[d];
            for (int i=0;i<g[d].size();++i)
                    s[g[d][i]]++;
            }
            s[v]=stop_w[v];
            for (int i=0;i<g[v].size();++i)
                s[g[v][i]]++;
        }
        cout << wynik;




    return 0;
}