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#include <algorithm>
#include <cstdio>
#include <numeric>
#include <unordered_set>
#include <vector>
#include <queue>
#include <utility>

#define ADD_EDGE(g, x, y) \
  do {\
    g[x].succs.insert(y);\
    g[y].preds.insert(x);\
  } while (0);

#define REMOVE_EDGE(g, x, y) \
  do {\
    g[x].succs.erase(y);\
    g[y].preds.erase(x);\
  } while (0);

struct vertex_st
{
  std::unordered_set<int> succs, preds;
  int dist1{}, dist2{}, path{};
  bool is_active = true;
};

using LL = long long;
using pair_ii = std::pair<int, int>;
using Graph = std::vector<vertex_st>;

/*
LL factorial(int n)
{
  LL res = 1;
  for (int i = 2; i <= n; i++) res *= i;
  return res;
}
*/

LL choose(int n, int k)
{
  LL res = 1;
  for (int i = n - k + 1; i <= n; i++) res *= i;
  for (int i = 2; i <= k; i++) res /= i;
  return res;
}

bool next_combination(int c[], int n, int k)
{
  int i = k - 1, j = -1, m = n;
  while (i >= 0) {
    if (c[i] < m) {
      j = i;
      break;
    }

    --i, --m;
  }

  if (j == -1) return false;

  ++c[j]; ++j;
  while (j < k) c[j] = c[j - 1] + 1, j++;
  return true;
}

int find_longest_path(const Graph& graph)
{
  int n = static_cast<int>(graph.size()) - 1;
  std::vector<int> paths(graph.size(), 1);

  for (int i = 1; i <= n; i++) {
    if (!graph[i].is_active) paths[i] = 0;
  }

  for (int i = n; i > 0; i--) {
    if (!graph[i].is_active) continue;
    for (auto v : graph[i].succs) {
      if (graph[v].is_active) {
        paths[i] = std::max(paths[i], paths[v] + 1);
      }
    }
  }

  return *std::max_element(begin(paths) + 1, end(paths));
}

void compute_paths(Graph& graph)
{
  int n = static_cast<int>(graph.size() - 1);

  for (int u = 1; u <= n; u++) {
    graph[u].dist1 = 1;
    graph[u].dist2 = 1;
    graph[u].path = 0;
  }

  for (int u = n; u > 0; u--) {
    if (!graph[u].is_active) continue;
    for (int v : graph[u].succs) {
      if (graph[v].is_active) {
        graph[u].dist1 = std::max(graph[u].dist1, graph[v].dist1 + 1);
      }
    }
  }

  for (int u = 1; u <= n; u++) {
    if (!graph[u].is_active) continue;
    for (int v : graph[u].preds) {
      if (graph[v].is_active) {
        graph[u].dist2 = std::max(graph[u].dist2, graph[v].dist2 + 1);
      }
    }
  }

  for (int v = 1; v <= n; v++) {
    if (graph[v].is_active) {
      graph[v].path = graph[v].dist1 + graph[v].dist2 - 1;
    }
  }
}

int solve(Graph& graph, int k)
{
  compute_paths(graph);

  int n = static_cast<int>(graph.size() - 1);
  std::vector<pair_ii> vertices;
  for (int v = 1; v <= n; v++) {
    if (graph[v].is_active) {
      vertices.push_back({ graph[v].path, v });
    }
  }

  if (vertices.empty()) return 0;

  int max_path = std::max_element(begin(vertices), end(vertices),
    [](const pair_ii& x, const pair_ii& y) { return x.first < y.first; })->first;

  if (k == 0) return max_path;

  int result = max_path;

  if (choose(n, k) <= 25000) {
    int n = static_cast<int>(graph.size() - 1);
    int c[4];
    std::iota(c, c + k, 1);

    do {
      bool skip = false;
      for (int i = 0; i < k; i++) if (!graph[c[i]].is_active) skip = true;
      if (skip) continue;

      for (int i = 0; i < k; i++) graph[c[i]].is_active = false;
      result = std::min(result, find_longest_path(graph));
      for (int i = 0; i < k; i++) graph[c[i]].is_active = true;
    } while (next_combination(c, n, k));
  }
  else {
    for (pair_ii& x : vertices) {
      if (x.first == max_path && graph[x.second].is_active) {
        graph[x.second].is_active = false;
        result = std::min(result, solve(graph, k - 1));
        graph[x.second].is_active = true;
      }
    }
  }

  return result;
}

int main()
{
  int n, m, k;
  std::scanf("%i %i %i", &n, &m, &k);

  Graph graph(n + 1);
  for (int i = 0; i < m; i++) {
    int x, y; std::scanf("%i %i", &x, &y);
    ADD_EDGE(graph, x, y);
  }
  graph[0].is_active = false;

  std::printf("%i\n", solve(graph, k));
}