#include <fstream>

using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
int e[1000001], i, j, n;
unsigned long long rasp;

int main()
{

    fin>>n;
    for(i=1; i<=n; ++i) e[i] = i;
    for(i=2; i<=n; ++i)
        if(e[i] == i ){
            --e[i];
            for(j=2; i*j<=n; ++j)
                e[i*j] = e[i*j] / i * (i-1);
        }
    rasp=n;
    for(i=2; i<=n; ++i)
        rasp = rasp + 1ll * (1 + 2*(e[i]-1));

    fout<<rasp;
    return 0;
}