#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
using namespace std;
using lint = long long int;
using P = pair<int, int>;
using PL = pair<lint, lint>;
#define FOR(i, begin, end) for(int i=(begin),i##_end_=(end);i<i##_end_;i++)
#define IFOR(i, begin, end) for(int i=(end)-1,i##_begin_=(begin);i>=i##_begin_;i--)
#define REP(i, n) FOR(i,0,n)
#define IREP(i, n) IFOR(i,0,n)
#define ALL(a)  (a).begin(),(a).end()
constexpr int MOD = 1000000007;
constexpr lint B1 = 1532834020;
constexpr lint M1 = 2147482409;
constexpr lint B2 = 1388622299;
constexpr lint M2 = 2147478017;
constexpr int INF = 2147483647;
void yes(bool expr) {cout << (expr ? "Yes" : "No") << "\n";}
template<class T>void chmax(T &a, const T &b) { if (a<b) a=b; }
template<class T>void chmin(T &a, const T &b) { if (b<a) a=b; }
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
int main()
{
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int N;
  cin >> N;
  vector<int> R(N);
  REP(i, N-1) cin >> R[i];
  REP(i, N-1) R[i]--;
  vector<int> d(N, 1e9);
  d[0] = 0;
  deque<int> que;
  que.push_back(0);
  while(!que.empty()) {
    int i = que.front();
    que.pop_front();
    if(i == N-1) break;
    if(d[i] + 1 < d[R[i]]) {
      chmin(d[R[i]], d[i] + 1);
      que.push_back(R[i]);
    }
    if(i > 0 && d[i] < d[i-1]) {
      chmin(d[i-1], d[i]);
      que.push_front(i-1);
    }
  }
  cout << d[N-1] << endl;
}