3.2.8

#include <iostream>
#include <cmath>

using namespace std;

int main()
{
    int n;
    double Sum=0;
    cin>>n;
    for (int i=1;i<=n;i++)
    {
        Sum+=(1.0/i)*(1.0/i);
    }

    cout<<Sum;
    return 0;
}