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

int n,v[1000000]={1},d,p;

int main()
{
ifstream f("fractii.in");
ofstream g("fractii.out");
f>>n;
v[1]=1;
for(int i=2;i<=n;i++)
  {
   int ci=i,d=2,s=1;
   while(d*d<=ci)
    {
     if(ci%d!=0) d++;
     else
      {
       while(ci%d==0)
        {
         ci/=d;
         s*=d;
        }
       s/=d;
       s=s*(d-1);
      }
    }
   if(ci>1) s=s*(ci-1);
   v[i]=2*s+v[i-1];
  }
g<<v[n];
}