#include<bits/stdc++.h>
using namespace std;
int main(){
  int n;
  cin >> n;
  vector<vector<pair<int,int>>> g(n);
  for(int i = 0;i < n - 1;i++){
  	int a;
    cin >> a;
    g[i].emplace_back(a - 1,1);
  }
  for(int i = 1;i < n;i++)g[i].emplace_back(i - 1,0);
  deque<int> que;
  que.emplace_front(0);
  vector<int> memo(n,1 << 30);
  memo[0] = 0;
  while(!que.empty()){
    int p = que.front();
    que.pop_front();
    for(auto [x,c] : g[p]){
      if(c == 0){
        if(memo[x] > memo[p]){
          memo[x] = memo[p];
          que.emplace_front(x);
        }
      }
      else{
        if(memo[x] > memo[p] + 1){
          memo[x] = memo[p] + 1;
          que.emplace_back(x);
        }
      }
    }
  }
  cout << memo.back() << "\n";
}