#include <fstream>
using namespace std;
const int a=1000001;
ifstream in("fractii.in");
ofstream out("fractii.out");
int v[a];
int main()
{
    int n,i,j,sol=0;
    in>>n;
    for(i=1;i<=n;i++)
    {
        v[i]=v[i]+i;
        sol=sol+2*v[i];
        for(j=2*i;j<=n;j=j+i)
            v[j]=v[j]-v[i];
    }
    out<<sol-1<<"\n";
    in.close();
    out.close();
}