#include <bits/stdc++.h>
using namespace std;
int main(){
  int N;
  cin >> N;
  vector<int> R(N - 1);
  for (int i = 0; i < N - 1; i++){
    cin >> R[i];
    R[i]--;
  }
  vector<vector<pair<int, int>>> E(N);
  for (int i = 0; i < N - 1; i++){
    E[i + 1].push_back(make_pair(0, i));
  }
  for (int i = 0; i < N - 1; i++){
    E[i].push_back(make_pair(1, R[i]));
  }
  vector<int> d(N, -1);
  deque<pair<int, int>> dq;
  dq.push_back(make_pair(0, 0));
  while (!dq.empty()){
    int c = dq.front().first;
    int v = dq.front().second;
    dq.pop_front();
    if (d[v] == -1){
      d[v] = c;
      for (auto P : E[v]){
        int w = P.second;
        if (d[w] == -1){
          if (P.first == 0){
            dq.push_front(make_pair(c, w));
          } else {
            dq.push_back(make_pair(c + 1, w));
          }
        }
      }
    }
  }
  cout << d[N - 1] << endl;
}