#include <iostream>
#include <queue>
#include<vector>
#include<set>
#include<stack>
#include<array>
#include<string>
#include <cassert>
#include <algorithm>
using namespace std;
#define ll long long 
#define endl "\n"
void solved(){
     int n;
     cin>>n;
     //vector<int> a(n+1);
     vector<array<int,2>> e[n+1];
     for(int i=1;i<=n-1;i++){
          int a;
          cin>>a;
          e[i].push_back({a,1});
     }
     for(int i=2;i<=n-1;i++) e[i].push_back({i-1,0});

     vector<int> dist(n+1,2e6);
     dist[1]=0;
     deque<int> q;
     q.push_back(1);
     while(q.size()){
         auto u=q.front();
         //cout<<u<<endl;
         q.pop_front();
         for(auto [v,cost]:e[u]){
            if(dist[u]+cost<dist[v]){
                dist[v]=dist[u]+cost;
                if(cost==1) q.push_back(v);
                else q.push_front(v);
            }
         }
     }
     cout<<dist[n]<<endl;

   

}
signed main(){
   
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);

    solved();
}