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#include <iostream>
#include <stdio.h>
#include <algorithm> 
using namespace std;

  const int MAX_NODES = 300;
  const int MAX_EDGES = 400;
  const int MAX_DELETIONS = 4;

  int nNodes;
  int nEdges;
  int nDeletions;
  int graph[MAX_EDGES][2];

  int deletions[MAX_DELETIONS];
  int chains[MAX_NODES];

  void prepareGraph() {
    cin >> nNodes;
    cin >> nEdges;
    cin >> nDeletions;

    for (int i = 0; i < nEdges; i++) {
      int from;
      cin >> from;
      from--;
      int to;
      cin >> to;
      to--;
      graph[i][0] = from;
      graph[i][1] = to;
    }
  }

  void sortGraph() {
    int coded[nEdges];
    for (int i = 0; i < nEdges; i++) {
      int from = graph[i][0];
      int to = graph[i][1];
      coded[i] = from * MAX_EDGES + to;
    }
    sort(coded, coded + nEdges);
    for (int i = 0; i < nEdges; i++) {
      graph[i][0] = coded[i] / MAX_EDGES;
      graph[i][1] = coded[i] % MAX_EDGES;
    }
  }

  void resetDeletions() {
    for (int i = 0; i < nDeletions; i++) {
      deletions[i] = i;
    }
  }

  /*
   * returns true if key was incremented or false if end of scope
   */
  bool incrementDeletions() {
    if (nDeletions == 0) {
      return false;
    }
    int keep;
    for (keep = 0; keep < nDeletions; keep++) {
      if (deletions[keep] == keep + (nNodes - nDeletions)) {
        break;
      }
    }
    if (keep == 0) {
      // we are at last combination
      return false;
    }

    deletions[keep - 1]++;
    for (int i = keep; i < nDeletions; i++) {
      deletions[i] = deletions[i - 1] + 1;
    }
    return true;
  }

  void forwardDeletions(int indexOfNode) {
    int keep = 0;
    for (int i = 0; i < nDeletions; i++) {
      if (deletions[i] < indexOfNode) {
        keep++;
      } else {
        break;
      }
    }
    // push remaining deletions to the right
    for (int i = keep; i < nDeletions; i++) {
      deletions[i] = i + (nNodes - nDeletions);
    }
  }

  bool isDeleted(int indexOfEdge) {
    for (int i = 0; i < nDeletions; i++) {
      if (deletions[i] == graph[indexOfEdge][0] || deletions[i] == graph[indexOfEdge][1]) {
        return true;
      }
    }
    return false;
  }

  /*
   * returns length of longest chain if it is shorter than limit
   *
   * or (node-nNodes) if (node) hit limit
   */
  int findLongestChain(int limit) {
    // clean chains
    for (int i = 0; i < nNodes; i++) {
      chains[i] = 1;
    }

    int longestChain = 1;
    for (int i = 0; i < nEdges; i++) {
      if (isDeleted(i)) {
        continue;
      }
      int nodeA = graph[i][0];
      int nodeB = graph[i][1];
      chains[nodeB] = max(chains[nodeB], chains[nodeA] + 1);
      longestChain = max(chains[nodeB], longestChain);

      if (longestChain >= limit) {
        // encode hitting limit as negative result
        return nodeB - nNodes;
      }
    }
    return longestChain;
  }

  int findResultByIterating(int limit) {
    int result = limit;
    resetDeletions();
    do {
      int response = findLongestChain(result);
      if (response < 0) {
        forwardDeletions(response + nNodes);
      } else {
        result = response;
      }
    } while (incrementDeletions());
    return result;
  }

  int findSolution() {
    if (nDeletions == 0) {
      return findLongestChain(1000);
    }
    if (nNodes == nDeletions) {
      return 0;
    }
    if (nDeletions <= 2) {
      return findResultByIterating(1000);
    }
    return findResultByIterating(1000);

  }

  int main() {
    prepareGraph();
    sortGraph();
    printf("%d", findSolution());
    return 0;
  }