#include <iostream>
#include <fstream>
#define NMAX 1000006

using namespace std;

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

long long fi[NMAX];

int main()
{
    long long N, suma=0;
    f >> N;
    for (int i = 1; i < NMAX; ++i)
        fi[i] = i;
   for (int i = 2; i < NMAX; ++i)
        if (fi[i] == i)
            for (int j = i; j < NMAX; j += i)
                fi[j] = fi[j] / i * (i - 1);
    for (int i=2; i<=N; i++)
    {
        suma+=fi[i];
    }
    suma=suma*2+1;
    g << suma;
    return 0;
}