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#include <algorithm>
#include <iostream>
#include <vector>


class Node
{
public:
    std::vector<short> parents;
    std::vector<short> children;
    bool removed;

    Node() : removed(false) {
        parents.reserve(10);
        children.reserve(10);
    }
};


int n;
int m;
int k;
std::vector<Node> nodes;
std::vector<short> sorted;
std::vector<int> scratch;


void LoadData()
{
    std::cin >> n >> m >> k;
    nodes.reserve(n);
    nodes.resize(n);
    for (int i = 0; i < m; i++) {
        short parent, child;
        std::cin >> parent >> child;
        nodes.at(parent-1).children.push_back(child-1);
        nodes.at(child-1).parents.push_back(parent-1);
    }
}


void TopoSort()
{
    sorted.reserve(n);
    std::vector<int> counts(n);
    for (int i = 0; i < n; i++) {
        counts[i] = nodes[i].parents.size();
    }
    for (int i = 0; i < n; i++) {
        bool found = false;
        for (int j = 0; j < n; j++) {
            if (counts[j] == 0) {
                found = true;
                counts[j] = -1;
                sorted.push_back(j);
                for (short child : nodes[j].children) {
                    --counts[child];
                }
            }
        }
        if (!found) break;
    }
}


int MaxPartialPathLength(std::vector<short> &indices)
{
    int result = 0;
    for (short i : indices) {
        int x = scratch[i];
        if (x > result) result = x;
    }
    return result;
}


int MaxPathLength()
{
    std::fill(scratch.begin(), scratch.end(), 0);
    for (short i : sorted) {
        if (nodes[i].removed) {
            scratch[i] = 0;
        } else {
            scratch[i] = MaxPartialPathLength(nodes[i].parents) + 1;
        }
    }
    return *std::max_element(scratch.begin(), scratch.end());
}


int FindBest(int start, int level, int initial)
{
    int result = initial;
    for (int i = start; i < n - level; i++) {
        nodes[i].removed = true;
        int x;
        if (level > 0) {
            x = FindBest(i + 1, level - 1, result);
        } else {
            x = MaxPathLength();
        }
        if (x < result) result = x;
        nodes[i].removed = false;
    }
    return result;
}


int main()
{
    LoadData();
    TopoSort();

    scratch.reserve(n);
    scratch.resize(n);
    int result = FindBest(0, k - 1, MaxPathLength());

    std::cout << result << '\n';
    return 0;
}