#include <iostream>
#include <fstream>

using namespace std;

int main(){
    
    ifstream in;
    ofstream out;
    
    int N, i, j;
    long long int sol = 0;
    
    in.open("fractii.in");    
    in >> N;
    in.close();
    
    int mult[N+1];
        
    for (i=2;i <= N;i++)
        mult[i] = i;
    
    for (i=2; i <= N; i++)
    {               
      if (mult[i] == i)
      {  
         for (j=i; j <= N; j += i)
         {
             mult[j] *= (i - 1);
             mult[j] /= i;
         }         
      }      
      sol += mult[i];                 
    }  
    
    out.open("fractii.out");
    sol = sol*2 + 1;
    out << sol;
    out.close();
    
    return 0;
}