115A - Party

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#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
int n, p, groupMax;
vector<int> manager;
vector<int> superior[2001];
void DFS(int m, int group) {
    groupMax = max(group, groupMax);
    for (int i = 0; i < superior[m].size(); ++i) {
        DFS(superior[m][i], group + 1);		
    }
}
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin >> n;
    for (int i = 1; i <= n; ++i) {
        cin >> p;
        if (p == -1) {
            manager.push_back(i);
        }
        else {
            superior[p].push_back(i);
        }
    }
    groupMax = 1;
    for (int i = 0; i < manager.size(); ++i) {
        DFS(manager[i], 1);
    }
    cout << groupMax << endl;
    return 0;
}