#include<stdio.h>
#define M 1000002
long m[M],n;
FILE *f=fopen("fractii.in","r");
FILE *g=fopen("fractii.out","w");

int main()
{long i,j;
 long long nrf;

 fscanf(f,"%ld",&n);

 for(i=1;i<=n;i++)
	m[i]=i;

  nrf=1;

 for(i=2;i<=n;i++)
  if(m[i]==i) for(j=i;j<=n;j=j+i)
		m[j]=m[j]/i*(i-1);

  for(i=2;i<=n;i++)
	nrf=nrf+2*m[i];

  fprintf(g,"%lld\n",nrf);
  fclose(f);
  fclose(g);
  return 0;}