#include <iostream>
#include <fstream>

using namespace std;

ifstream fin("fractii.in");
ofstream fout("fractii.out");
int phi(int n)
{
    int r = n , d = 2;
    while(n > 1)
    {
        if(n % d == 0)
        {
            r = r / d * (d - 1);
            while(n % d == 0)
                n /= d;
        }
        d ++;
        if(d * d > n)
            d = n;
    }
    return r;
}
int main()
{int n;
long long unsigned int ok=-1;
    fin>>n;
    for(int i=1;i<=n;i++)
    {ok=ok+2*phi(i);
    }
    fout<<ok;
fin.close();
fout.close();
    return 0;
}