#include <fstream>

using namespace std;

const int N=1000005;

ifstream fin("fractii.in");
ofstream fout("fractii.out");

int a[N];

int main()
{
    int n, i, j;
    long long sol=0;
    fin>>n;
    for(i=1;i<=n;i++)
    {
        a[i]+=i;
        sol+=2*a[i];
        for(j=2*i;j<=n;j+=i) a[j]-=a[i];
    }
    fout<<sol-1<<"\n";
    fin.close();
    fout.close();
}