#include<fstream.h>   
long long unsigned int n,i,j,v[200000],nr=0;   
ifstream f("fractii.in");   
ofstream g("fractii.out");   
int main()   
{   
f>>n;   
for(i=2;i<=n;i++)v[i]=0;   
for(i=2;i<=n;i++)   
    if(v[i]!=0)nr=nr+v[i];   
   else  
    {   
      nr=nr+i-1;   
      for(j=2*i;j<=n;j+=i)   
        if(v[j]) v[j]=v[j]-v[j]/i;   
         else v[j]=j-j/i;   
      }   
g<<(2*nr+1);   
f.close();   
g.close();   
return 0;   
}