#include <bits/stdc++.h>
using namespace std;
using namespace std;
long long int **sparse;
void buildSparseTable(long long int arr[], long long int n,
                      long long int **sparse) {
  for (long long int i = 0; i < n; i++) {
    sparse[i][0] = i;
  }
  for (long long int j = 1; pow(2, j) <= n; j++) {
    for (long long int i = 0; i + pow(2, j) - 1 < n; i++) {
      if (arr[sparse[i][j - 1]] >=
          arr[sparse[i + (long long int)pow(2, j - 1)][j - 1]]) {
        sparse[i][j] = sparse[i][j - 1];
      } else {
        sparse[i][j] = sparse[i + (long long int)pow(2, j - 1)][j - 1];
      }
    }
  }
}
long long int query(long long int l, long long int r, long long int **sparse,
                    long long int arr[]) {
  long long int len = r - l + 1;
  long long int k = (log(len) / log(2.0));
  long long int m;
  if (arr[sparse[l][k]] >= arr[sparse[l + len - (long long int)pow(2, k)][k]]) {
    return sparse[l][k];
  } else
    return sparse[l + len - (long long int)pow(2, k)][k];
}
int main() {
  long long int n;
  cin >> n;
  long long int arr[n];
  sparse = new long long int *[n];
  for (long long int i = 0; i < n; i++) {
    sparse[i] = new long long int[(long long int)floor(log(n) / log(2.0)) + 1];
  }
  arr[n - 1] = n - 1;
  for (long long int i = 0; i < n - 1; i++) {
    cin >> arr[i];
    arr[i]--;
  }
  buildSparseTable(arr, n, sparse);
  long long int dp[n];
  dp[n - 1] = 0;
  long long int sum = 0;
  for (long long int i = n - 2; i >= 0; i--) {
    long long int m = query(i + 1, arr[i], sparse, arr);
    dp[i] = dp[m] - (arr[i] - m) + n - 1 - i;
    sum += dp[i];
  }
  cout << sum << endl;
}
