#include <fstream>
using namespace std;
#define MAX 1000005
FILE *f=fopen("fractii.in","r");
FILE *g=fopen("fractii.out","w");
long v[MAX];
int main()
{
    long long n,i,j,nr=0;

	fscanf(f,"%lld",&n);
	for (i=1;i<=n;i++)
	 v[i]=i;
	for (i=2;i<=n;i++)
     if (v[i]==i)
      for (j=i;j<=n;j+=i)
        v[j] /=i, v[j] *= (i-1);
	for (i=2;i<=n;i++)
 	 nr+=v[i];
	fprintf(g,"%lld",nr*2+1);
	fclose(f);
	fclose(g);
	return 0;
}