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#include <vector>
#include <queue>
#include <algorithm>
#include <stdio.h>

using namespace std;

#define FOR_EACH(i,c) for(__typeof((c).begin()) i=(c).begin(); i!=(c).end(); ++i)

#define DBG(X) X
#define NOOP(X) 

#define VERTEX_NUMBER_TYPE int

void print_vector(vector<VERTEX_NUMBER_TYPE> v) {
  for (int i=0; i < v.size(); i++) {
    printf("%d ", v[i]);
  }
  printf("\n");
}

struct Vertice {
  vector<VERTEX_NUMBER_TYPE> outEdges_;
  vector<VERTEX_NUMBER_TYPE> inEdges_;
};

struct Graph {

  vector<Vertice> vertices_;
  VERTEX_NUMBER_TYPE *dist;

  Graph(VERTEX_NUMBER_TYPE n) {
    vertices_.resize(n);
    dist = new VERTEX_NUMBER_TYPE[n];
  }

  ~Graph() {
    delete [] dist;
  }

  void addEdge(VERTEX_NUMBER_TYPE a, VERTEX_NUMBER_TYPE b) {
    vertices_[a].outEdges_.push_back(b);
    vertices_[b].inEdges_.push_back(a);
  }

  //bool forbidden1(const vector<int>& frb_vec, int v) {
  //  return std::find(frb_vec.begin(), frb_vec.end(), v) != frb_vec.end();
  //}

  inline bool forbidden2(VERTEX_NUMBER_TYPE frb_vec[4], VERTEX_NUMBER_TYPE v) {
    /*register VERTEX_NUMBER_TYPE* frb_end = frb_vec + 4;
    register VERTEX_NUMBER_TYPE* frb_begin = frb_vec;
    while (frb_begin < frb_end) {
      if (*frb_begin++ == v) {
        return true;
      }
    }
    return false;*/
    return (v == frb_vec[0] || v == frb_vec[1] || v == frb_vec[2] || v == frb_vec[3]);
  }

  vector<VERTEX_NUMBER_TYPE> topSort(const vector<VERTEX_NUMBER_TYPE>& frb_vec)  {
    queue<VERTEX_NUMBER_TYPE> Q;
    VERTEX_NUMBER_TYPE n = vertices_.size();
    VERTEX_NUMBER_TYPE inDegree[n];
    for(VERTEX_NUMBER_TYPE i=0; i < n; i++) {
      inDegree[i] = vertices_[i].inEdges_.size();
      // NOOP(FOR_EACH(edge, vertices_[i].inEdges_) {if (forbidden(frb_vec, *edge)) {--inDegree[i]; });});
      if(inDegree[i] == 0)  {
        Q.push(i);
      }
    }
    vector<VERTEX_NUMBER_TYPE> res;
    while(!Q.empty())  {
      VERTEX_NUMBER_TYPE curr_v = Q.front();
      Q.pop();
      //NOOP(if (forbidden(frb_vec, curr_v)) continue;);
      res.emplace_back(curr_v);
      FOR_EACH(it, vertices_[curr_v].outEdges_) {
        VERTEX_NUMBER_TYPE next_v = *it;
        //NOOP(if (forbidden(frb_vec, next_v)) continue;);
        if(inDegree[next_v] > 0)  {
          inDegree[next_v]--;
          if(inDegree[next_v] == 0) {
            Q.push(next_v);
          }
        }
      }
    }
    return res;
  }

  int longestPath(const vector<VERTEX_NUMBER_TYPE>& tsorted, VERTEX_NUMBER_TYPE frb_vec[4], VERTEX_NUMBER_TYPE pruningValue) {
    //DBG(print_vector(forbidden));

    VERTEX_NUMBER_TYPE longestPath = 0;
    for (VERTEX_NUMBER_TYPE i=0; i < tsorted.size(); i++) {
      VERTEX_NUMBER_TYPE curr_v = tsorted[i];
      dist[curr_v] = 0;
      if (forbidden2(frb_vec, curr_v)) {
        continue;
      }
      
      FOR_EACH(it, vertices_[curr_v].inEdges_) {
        VERTEX_NUMBER_TYPE before_v = *it;
        if (forbidden2(frb_vec, before_v)) {
          continue;
        }
        VERTEX_NUMBER_TYPE new_dist = dist[before_v] + 1;
        if (new_dist > dist[curr_v]) {
          dist[curr_v] = new_dist;
        }
      }
      VERTEX_NUMBER_TYPE currentDist = dist[curr_v];
      if (currentDist > longestPath) {
        longestPath = currentDist;
        if (longestPath >= pruningValue) {
          return longestPath;
        }
      }
    }
    return longestPath;
  }

  int longestPathWithRandomKRemoved(int k, const vector<VERTEX_NUMBER_TYPE>& tsorted, VERTEX_NUMBER_TYPE frb_vec[4], VERTEX_NUMBER_TYPE currentBest) {
    frb_vec[0] = -1;
    frb_vec[1] = -1;
    frb_vec[2] = -1;
    frb_vec[3] = -1;
    int frb_vec_size = 0;
    int n = vertices_.size();
    while (frb_vec_size < k) {
      int rv = std::rand() % n;
      if (!forbidden2(frb_vec, rv)) {
        frb_vec[frb_vec_size++] = rv;
      }
    }

    return longestPath(tsorted, frb_vec, currentBest-1) + 1;
  }
};

int main() {
  std::srand(0);
  int n,m,k;
  scanf("%d%d%d", &n, &m, &k);
  Graph G(n);
  for (int i=0; i < m; i++) {
    int x,y;
    scanf("%d%d", &x, &y);
    G.addEdge(x-1,y-1);
  }
  if (k >= n) {
    printf("0\n");
    return 0;
  }

  VERTEX_NUMBER_TYPE frb_vec_memholder[4];
  for (int i=0; i < 4; i++) frb_vec_memholder[i] = -1;

  vector<VERTEX_NUMBER_TYPE> tsorted = G.topSort(vector<VERTEX_NUMBER_TYPE>{});
  
  // print_vector(tsorted);
  int initialLongestPath = G.longestPath(tsorted, frb_vec_memholder, 30000) + 1;
  if (k == 0) {
    printf("%d\n", initialLongestPath);
    return 0; 
  }
  int bestRes = initialLongestPath;
  
  for (int i=0; i < 500000; i++) {
    int res = G.longestPathWithRandomKRemoved(k, tsorted, frb_vec_memholder, bestRes);
    bestRes = min(bestRes, res);
    //printf("longestRandom=%d best=%d\n", res, bestRes);
  }
  printf("%d\n", bestRes);
  return 0;
}