#include <fstream.h>
  
ifstream f("fractii.in");
ofstream g("fractii.out");
  
long long unsigned int s=0,a[1000000],j,n,i;
  
int main()
{   
	f>>n;
  
    for(i=2;i<=n;i++)
        if(!a[i])
        {
            s+=i-1;
  
            for(j=i*2;j<=n;j+=i)
                if(a[j])    a[j]-=a[j]/i;
                else a[j]=j-j/i;
        }
        else s+=a[i];
  
    g<<2*s+1;
  
	return 0;
}