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

using namespace std;

struct Vertex {
  vector<int> links;
  int value = -1;
  int bestNext = -1;
  bool removed = false;
  void clearCache() {
    value = bestNext = -1;
  }
};

class Solution {
 private:
  int n, m, k;
  vector<Vertex> vertexMap;

  int getVertexIdWithLongestPath() {
    int resultId = -1, resultValue = 0;
    for (int id = 0; id < vertexMap.size(); id++) {
      int value = getVertexValue(id);
      if (value == -1) continue;
      if (resultId == -1 || value > resultValue) {
        resultId = id;
        resultValue = value;
      }
    }
    return resultId;
  }

  int getVertexIdWithLongestPath(const vector<int>& idSubset) {
    int resultId = -1, resultValue = 0;
    for (int id : idSubset) {
      int value = getVertexValue(id);
      if (value == -1) continue;
      if (resultId == -1 || value > resultValue) {
        resultId = id;
        resultValue = value;
      }
    }
    return resultId;
  }

  int getVertexValue(int id) {
    Vertex& v = vertexMap[id];
    if (v.removed) return -1;
    if (v.value == -1) {
      v.bestNext = getVertexIdWithLongestPath(v.links);
      v.value = v.bestNext == -1 ? 0 : vertexMap[v.bestNext].value + 1;
    }
    return v.value;
  }

  void clearCache() {
    for (int id = 0; id < vertexMap.size(); id++) vertexMap[id].clearCache();
  }

  void expandPath(int fromId, vector<int>& result) {
    result.clear();
    if (fromId < 0) return;
    result.reserve(vertexMap[fromId].value);
    for (int id = fromId; id != -1; id = vertexMap[id].bestNext)
      result.push_back(id);
  }

  int alternativeLength(int id, int bestId) {
    Vertex& v = vertexMap[id];
    int altVal = 0;
    for (int linkId : v.links) {
      if (linkId == bestId) continue;
      int val = getVertexValue(linkId);
      if (val > altVal) altVal = val + 1;
    }
    return altVal;
  }

  int solve(int removeCount) {
    int startId = getVertexIdWithLongestPath();
    if (startId == -1) return 0;
    int result = vertexMap[startId].value + 1;

    if (removeCount > 0) {
      vector<int> path;
      expandPath(startId, path);

      vector<vector<int>> altLengths(n + 1);
      altLengths[path.size() - 1].push_back(path[0]);

      for (int id, len, i = 1; i < path.size(); i++) {
        id = path[i];
        len = max<int>(path.size() - i - 1, i + alternativeLength(id - 1, id));
        altLengths[len].push_back(id);
      }

      for (int i = 0; i < altLengths.size(); i++) {
        if (i >= result) break;
        for (int id : altLengths[i]) {
          vertexMap[id].removed = true;
          clearCache();
          int subResult = solve(removeCount - 1);
          if (subResult < result) result = subResult;
          vertexMap[id].removed = false;
        }
      }
    }
    return result;
  }

 public:
  void readInput() {
    cin >> n;
    cin >> m;
    cin >> k;
    vertexMap.resize(n);
    for (int from, to, i = 0; i < m; i++) {
      cin >> from;
      cin >> to;
      vertexMap[from - 1].links.push_back(to - 1);
    }
  }

  int solve() {
    return solve(k);
  }
};

int main(void) {
  Solution solution;
  solution.readInput();
  cout << solution.solve();
  return 0;
}