#include <fstream>
#define nmax 1000000

using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
unsigned long long N, nrFrc;
int v[nmax];
int main()
{unsigned i, j, S = 0;
    f>>N;

    for (i = 1; i<= N; i++) v[i] = i;

    for (i=2;i<=N;i++)
        if (v[i] == i)
            for (j = i; j <= N; j += i){
                v[j] /=i;
                v[j] *= (i - 1);
            }

    for(i = 2; i <= N; ++i)
        S +=v[i];

        g<<2 * S + 1<<'\n';
    return 0;
}