Example

Input

4
1 1 2


Output

6
#define  _CRT_SECURE_NO_WARNINGS
#pragma comment (linker, "/STACK:526000000")

#include "bits/stdc++.h"

using namespace std;
typedef string::const_iterator State;
#define eps 1e-11L
#define MAX_MOD 1000000007LL
#define GYAKU 500000004LL

#define MOD 998244353LL
#define seg_size 262144 * 4LL
#define pb push_back
#define mp make_pair
typedef long long ll;
#define REP(a,b) for(long long (a) = 0;(a) < (b);++(a))
#define ALL(x) (x).begin(),(x).end()

void init() {
    iostream::sync_with_stdio(false);
    cout << fixed << setprecision(20);
}


#define int ll

unsigned long xor128() {
    static unsigned long x = 123456789, y = 362436069, z = 521288629, w = 88675123;
    unsigned long t = (x ^ (x << 11));
    x = y; y = z; z = w;
    return (w = (w ^ (w >> 19)) ^ (t ^ (t >> 8)));
}

int depth[200000];
vector<int> vertexs[200000];
int back[30][200000];
void dfs(int now) {
    for (auto x : vertexs[now]) {
        depth[x] = depth[now] + 1;
        back[0][x] = now;
        dfs(x);
    }
}
int lca(int a, int b) {
    if (depth[a] > depth[b])swap(a, b);
    int ans = 0;
    for (int q = 20; q >= 0; --q) {
        if (depth[a] <= depth[b] - (1 << q)) {
            ans += 1 << q;
            b = back[q][b];
        }
    }
    for (int q = 20; q >= 0; --q) {
        if (back[q][a] != back[q][b]) {
            ans += 1 << (q + 1);
            a = back[q][a];
            b = back[q][b];
            q++;
        }
    }
    if (a != b) ans += 2;
    return ans;
}
void solve() {
    int n;
    cin >> n;
    REP(i, n-1) {
        int a;
        cin >> a;
        vertexs[a - 1].push_back(i + 1);
    }
    dfs(0);
    for (int q = 1; q < 30; ++q) {
        REP(i, n) {
            back[q][i] = back[q - 1][back[q-1][i]];
        }
    }
    queue<int> next;
    int backing = 0;
    next.push(0);
    int ans = 0;
    while (next.empty() == false) {
        int now = next.front();
        next.pop();
        ans += lca(now, backing);
        backing = now;
        for (auto x : vertexs[now]) {
            next.push(x);
        }
    }
    cout << ans << endl;
}

#undef int
int main() {
    init();
    solve();
}

