#include<fstream>

using namespace std;
long long suma,n;
int phi[1000005]; 
   
int main(){
    ifstream f1("fractii.in");
    ofstream f2("fractii.out");
    f1>>n;
    long i,j,k;
    for (i=1; i<=n;i++) phi[i]=i;
    
    for (i=2; i<=n; i++)
        if (phi[i]==i)
          for (j=i, k=1;j<=n; j+=i,k++)
               phi[j]=k*(i-1);
     
    suma=0;
    for (i=2; i<=n; i++) suma+=phi[i];
    suma*=2;
    suma++;   
    f2<<suma;
    f1.close();
    f2.close();
    return 0;}