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

class TreeHeight {
  int n;             
  std::vector<int> parent;

public:
  void read() {
    std::cin >> n;
    parent.resize(n);
    for (int i = 0; i < n; i++)
      std::cin >> parent[i];
  }

  int compute_height() {
    // Replace this code with a faster implementation
    int maxHeight = 0;
    for (int vertex = 0; vertex < n; vertex++) {
      int height = 0;
      for (int i = vertex; i != -1; i = parent[i])
        height++;
      maxHeight = std::max(maxHeight, height);
    }
    return maxHeight;
  }
};

int main() {
  std::ios_base::sync_with_stdio(0);
  TreeHeight tree;
  tree.read();
  std::cout << tree.compute_height() << std::endl;
}