#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <math.h>
#include <limits.h>
#define Max(a, b) ((a) > (b) ? (a) : (b))
#define Min(a, b) ((a) > (b) ? (b) : (a))
#define abs(x) ((x) > 0 ? (x) : -(x))
#define rep(i, n) for(int i = 0; i < (n); i++)
#define INF 1000000000000 //10^12
#define MOD 1000000007 //10^9 + 7
#define endl printf("\n")
typedef long long ll;

#define MAX_N  300010

ll n, dat[2 * MAX_N - 1];

void
init(ll n_)
{
  n = 1;
  while (n < n_) {
    n *= 2;
  }

  for (int i = 0; i < 2 * n - 1; i++) {
    dat[i] = 0;
  }
}

void
update(ll k, ll a)
{
  k += n - 1;
  dat[k] += a;

  while (k > 0) {
    k = (k - 1) / 2;
    dat[k] = dat[2 * k + 1] + dat[2 * k + 2];
  }
}

//[a, b)の和を求める
int
query(ll a, ll b, ll k, ll l, ll r)
{
  if (r <= a || b <= l) {
    return 0;
  }

  if (a <= l && r <= b) {
    return dat[k];
  } else {
    ll vl = query(a, b, k * 2 + 1, l, (l + r) / 2);
    ll vr = query(a, b, k * 2 + 2, (l + r) / 2, r);
    return vl + vr;
  }
}

typedef struct { ll u, v; } E;

int
asort(const void *a, const void *b)
{
  E x = *(E *)a, y = *(E *)b;
  if (x.u > y.u) return  1;
  if (x.u < y.u) return -1;
  return 0;
}

ll cnt = 0;

void
dfs(ll i, E *e, ll *id)
{
  update(i, 1);
  cnt += query(0, i, 0, 0, n);
  for (ll j = id[i]; j < id[i + 1]; j++) {
    if (dat[n - 1 + e[j].v] == 0) {
      dfs(e[j].v, e, id);
    }
  }
  update(i, -1);
  return;
}
  
int
main(int argc, char **argv)
{
  ll m;
  scanf("%lld", &m);

  E e[300010];
  ll a; 
  for (int i = 1; i < m; i++) {
    scanf("%lld", &a);
    e[i - 1].u = a;
    e[i - 1].v = i;
  }

  qsort(e, m - 1, sizeof(E), asort);
  
  ll id[300010];
  id[0] = 0;

  ll p = 0;
  for (ll i = 0; i < m; i++){
    while(e[p].u < i && p < m - 1) p++;
    id[i] = p;
  }
  

  id[m] = m - 1;

  init(m);
  dfs(0, e, id);

  printf("%lld\n", cnt);

  return 0;
}