Example

Input

4
1 1 2


Output

6
/* template.cpp {{{ */
#include <bits/stdc++.h>
using namespace std;
#define get_macro(a, b, c, d, name, ...) name
#define rep(...) get_macro(__VA_ARGS__, rep4, rep3, rep2, rep1)(__VA_ARGS__)
#define rrep(...) get_macro(__VA_ARGS__, rrep4, rrep3, rrep2, rrep1)(__VA_ARGS__)
#define rep1(n) rep2(i_, n)
#define rep2(i, n) rep3(i, 0, n)
#define rep3(i, a, b) rep4(i, a, b, 1)
#define rep4(i, a, b, s) for (ll i = (a); i < (ll)(b); i += (ll)(s))
#define rrep1(n) rrep2(i_, n)
#define rrep2(i, n) rrep3(i, 0, n)
#define rrep3(i, a, b) rrep4(i, a, b, 1)
#define rrep4(i, a, b, s) for (ll i = (ll)(b) - 1; i >= (ll)(a); i -= (ll)(s))
#define each(x, c) for (auto &&x : c)
#define fs first
#define sc second
#define all(c) begin(c), end(c)
using ui = unsigned;
using ll = long long;
using ul = unsigned long long;
using ld = long double;
const int inf = 1e9 + 10;
const ll inf_ll = 1e18 + 10;
const ll mod = 1e9 + 7;
const ll mod9 = 1e9 + 9;
const int dx[]{-1, 0, 1, 0, -1, 1, 1, -1};
const int dy[]{0, -1, 0, 1, -1, -1, 1, 1};
template<class T, class U> void chmin(T &x, const U &y){ x = min<T>(x, y); }
template<class T, class U> void chmax(T &x, const U &y){ x = max<T>(x, y); }
struct prepare_ { prepare_(){ cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(12); } } prepare__;
/* }}} */

int n;
vector<int> g[100000];
int p[20][100000];
int d[100000];
vector<int> ord;

int main(){
  memset(p, -1, sizeof(p));
  cin >> n;
  rep(i, 1, n){
    int x;
    cin >> x, x--;
    g[x].push_back(i);
    p[0][i] = x;
    d[i] = d[x] + 1;
  }
  rep(i, 19) rep(j, n) p[i + 1][j] = p[i][j] != -1 ? p[i][p[i][j]] : -1;
  queue<int> q;
  ord.push_back(0);
  q.push(0);
  while (q.size()){
    int v = q.front(); q.pop();
    each(u, g[v]){
      ord.push_back(u);
      q.push(u);
    }
  }
  ll res = 0;
  int v = 0;
  each(u, ord){
    int x = v, y = u;
    if (d[x] < d[y]) swap(x, y);
    rep(i, 20) if (d[x] - d[y] >> i & 1) x = p[i][x];
    rrep(i, 20) if (p[i][x] != p[i][y]) x = p[i][x], y = p[i][y];
    if (x != y) x = p[0][x];
    res += d[u] + d[v] - d[x] * 2;
    v = u;
  }
  cout << res << endl;
}