#nullable enable

#region
var _input = Array.Empty<string>();
var _iter = 0;
string String()
{
    while (_iter >= _input.Length) (_input, _iter) = (Console.ReadLine()!.Split(' '), 0);
    return _input[_iter++];
}
T I<T>() where T : IParsable<T> => T.Parse(String(), null);
#endregion

T[] Range<T>(int n, Func<T> F) => Enumerable.Range(0, n).Select(_ => F()).ToArray();

var n = I<int>();
var pz = Range(n, () => I<int>() - 1);

var ip = new bool[n];
ip.AsSpan().Fill(true);
var l = Range(n, () => new List<int>());
for (var i = 0; i < n; i++)
{
    var p = pz[i];
    if (p >= 0)
    {
        l[i].Add(p);
        ip[p] = false;
    }
}
var ans = 0;
void S(int d, int v)
{
    if (d == 2) ans++;
    foreach (var next in l[v]) S(d + 1, next);
}
for (var i = 0; i < n; i++) if (ip[i]) S(0, i);
Console.WriteLine(ans);