#include <iostream>
using namespace std;

double sum(int n)
{
    if (n < 1)
        return 0.0;
    else
        return pow(-1, n) / n + sum(n - 1);
}

int main()
{
    int n;
    cout << "n = ";
    cin >> n;

    double res = sum(n);
    cout << res << endl;
}