#include <iostream>
#include <fstream>
#include <bits/stdc++.h>

using namespace std;

ifstream f("fractii.in");
ofstream g("fractii.out");

int main()
{
    int n;
    f >> n;
    float fractii,ct=0;
    bool prim[n+1];
    memset(prim, true, sizeof(prim));
    for (int p=2; p*p<=n; p++)
    {
        if (prim[p] == true)
        {
            for (int i=p*2; i<=n; i += p)
                prim[i] = false;
        }
    }
    for(int i=1;i<=n;i++){
        fractii=i;
        for (int p=2; p<=n; p++)
           if (prim[p]&&i%p==0)
             fractii*=1-1/(float)p;
        ct+=fractii;
    }
    g << ct*2-1;
}