#include <iostream>
#include <fstream>

using namespace std;

ifstream fin("fractii.in");
ofstream fout("fractii.out");

bool prim[1000000];
float sub[100000];
long long rez = 4;
double partial;

int main()
{
    int n;

    fin>>n;

    prim[1] = true;
    for(int i=2; i<=n; i++){
        if(!prim[i]){
                for(int k=i+i; k<=n; k += k)
                prim[k] = true;
        }
    }

    for(int i=4; i<=n; i++){
            partial = i;
            for(int j=2; j<=i; j++){
                if(!prim[j] && i % j == 0) partial *= (1 - (float)1/j);
            }
            rez += partial;
    }

    fout<<(rez*2)-1;
    return 0;
}