#include <iostream>
#include <fstream>
using namespace std;

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

    int n,i,j,r,ct=0,aux1,aux2;
    f>>n;
    int v[n+1];
    for(i=1;i<=n;i++)
        v[i]=i;
    for(i=2;i<=n;i++)
       {   if(v[i]==i)
              {
                  v[i]--;
                  for(j=2;j*i<=n;j++)
                      v[j*i]=v[j*i]/i*(i-1);

              }
      }
    for(i=1;i<=n;i++)
       ct+=v[i];
    g<<2*ct-1;
    return 0;
}