#include <fstream>
using namespace std;
#define maxN 1000005
ifstream in("fractii.in");
ofstream out("fractii.out");
int n;
int getthem[maxN];
void reading()
{
    in>>n;
}
void init_ciur()
{
    int i;
    for(i=1;i<=n;i++)
    {
        getthem[i]=i;
    }
}
void lets_see()
{
    int i,j;
    for(i=2;i<=n;i++)
        if(getthem[i]==i)
            for(j=i;j<=n;j+=i)
            {
                getthem[j]=getthem[j]/i;
                getthem[j]=getthem[j]*(i-1);
            }
}
long long get_fractions_number()
{
    long long number_of_fractions=1;
    for(int i=2;i<=n;i++)
        number_of_fractions+=1LL*getthem[i]*2;
    return number_of_fractions;
}
int main()
{
    reading();
    init_ciur();
    lets_see();
    out<<get_fractions_number();
    in.close();
    out.close();
    return 0;
}