#include <iostream>
using namespace std;

int main()
{
    double summary = 0;
    int N;

    cout << "Enter the amount of elements(N): ";
    cin >> N;

    for (int i = 0; i < N; i++)
    {
        double temp = 1.0 / double((i + 1) * (i + 1) * (i + 1));
        summary += temp;
    }

    cout << endl << "Your summary is " << summary << endl;
    return 0;
}