#include <iostream>

using namespace std;

int main()
{
    int K;
    cin >> K;
    int num[K], max = 1;
    for (int i = 0; i < K; ++i)
    {
        cin >> num[i];
    }

    for (int i = 0; i < K; ++i)
    {
        if (num[i] != -1)
        {
            int cnt = 0, cur = i;
            while (num[cur] != -1)
            {
                int tmp = cur;
                cnt++;
                cur = num[cur] - 1;
                num[tmp] = -1;
            }
            if (cnt > max)
            {
                max = cnt;
            }
        }
    }

    cout << max << endl;
}