#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using ld = long double;
using mint = modint998244353;

struct edge {
  int to, cost;
};
const int INF = 1e9;

int main() {
  int N; cin >> N;
  vector<vector<edge>> G(N);
  for (int i = 0; i < N - 1; i++) {
    int a; cin >> a;
    G[i].push_back({a - 1, 1});
  }
  for (int i = 1; i < N; i++) G[i].push_back({i - 1, 0});
  vector<int> dist(N, INF); dist[0] = 0;
  deque<int> que; que.push_back(0);
  while (!que.empty()) {
    int v = que.front(); que.pop_front();
    for (edge e: G[v]) {
      if (dist[e.to] > dist[v] + e.cost) {
        dist[e.to] = dist[v] + e.cost;
        if (e.cost == 1) que.push_back(e.to);
        else que.push_front(e.to);
      }
    }
  }
  cout << dist[N - 1] << endl;
  return 0;
}