#include <bits/stdc++.h>
#define REP(i, s, n) for (int i = s; i < n; i++)
#define ALL(a) a.begin(), a.end()
#define MOD 1000000007
using namespace std;
typedef long long ll;

template <typename T>
class BIT {
   public:
    BIT(int n) : N(n), A(n + 1, 0) {}

    T sum(int i) {
        T res = 0;
        while (i > 0) {
            res += A[i];
            i -= i & (-i);
        }
        return res;
    }

    T sum(int i, int j) {
        return sum(j) - sum(i - 1);
    }

    void add(int i, T x) {
        while (i <= N) {
            A[i] += x;
            i += (i & (-i));
        }
    }

   private:
    vector<T> A;
    int N;
};

ll dfs(BIT<int> &B, vector<vector<int>> &G, int n) {
    // cout << "# looking at : " << n << endl;
    B.add(n + 1, 1);
    ll ret = 0;
    for (auto g : G[n]) {
        ret += B.sum(g + 1);
        ret += dfs(B, G, g);
    }
    B.add(n + 1, -1);
    return ret;
}

int main() {
    int N; cin >> N;
    vector<vector<int>> G(N);
    REP(i, 1, N) {
        int a; cin >> a;
        G[a].push_back(i);
    }

    BIT<int> bit(N);
    cout << dfs(bit, G, 0) << endl;

    return 0;
}