#include<fstream.h>

long unsigned int n,i,j,v[1000000],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]/i;
         else v[j]=j-j/i;
      }
g<<(2*nr+1);
f.close();
g.close();
return 0;
}