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#include <bits/stdc++.h>
using namespace std;

#define st first
#define nd second
typedef pair < int, int > PII;
typedef long long LL;

const int N = 300 + 7, LIMIT = 72e4;
const LL M = 1e9 + 7LL;

vector < int > G[N];
bool Blocked[N];
int In[N], D[N], T[N];
queue < int > Q;
LL H[N];
unordered_set < LL > S;

int n, k, result, calls;

int Bfs ()
{   
    for (int i = 1; i <= n; ++i)
        T[i] = In[i],
        D[i] = 1;

    for (int i = 1; i <= n; ++i)
        if (Blocked[i])
            for (int s : G[i])
                --T[s];
    
    for (int i = 1; i <= n; ++i)
        if (!T[i] && !Blocked[i])
            Q.push(i);

    int maxi = 0;

    while (!Q.empty())
    {
        int v = Q.front();
        Q.pop();

        int d = D[v];
        maxi = max(maxi, d);

        for (int s : G[v])
        {
            if (Blocked[s])
                continue;

            D[s] = max(D[s], d + 1);
            if (--T[s] == 0)
                Q.push(s);
        }
    }

    return maxi;
}

bool Go (int r, LL h)
{   
    if (S.find(h) != S.end())  
        return true;
    S.insert(h);

    ++calls;

    if (r == 0)
    {
        result = min(result, Bfs());
        return true;
    }

    if (calls > LIMIT)
        return false;

    int maxi = Bfs();   
    vector < PII > V;
    
    for (int i = 1; i <= n; ++i)
        if (!Blocked[i])
            V.push_back({abs(2 * D[i] - result - 1), i});
    sort(V.begin(), V.end());

    for (int i = 0; i < V.size(); ++i)
    {
        Blocked[V[i].nd] = true;
        if (!Go(r - 1, (h * H[V[i].nd]) % M))
            return false;
        Blocked[V[i].nd] = false;
    }

    return true;
}

void Read ()
{
    int m;
    scanf("%d %d %d", &n, &m, &k);

    for (int i = 0; i < m; ++i)
    {
        int u, v;
        scanf("%d %d", &u, &v);
        
        ++In[v];
        G[u].push_back(v);
    }
}

void Solve ()
{
    for (int i = 1; i <= n; ++i)
        H[i] = rand() % (M - 2LL) + 2LL;

    result = n;
    Go(k, 1LL);
    printf("%d", result);
}

int main ()
{
    srand(time(NULL));

    Read();
    Solve();

    return 0;
}