#include<stdio.h>
#define M 1000010
FILE *f=fopen("fractii.in","r");
FILE *g=fopen("fractii.out","w");
 
long m[M],n;

int main()
{long i,j;
 long long nr=1;
 
 fscanf(f,"%ld",&n);
 
 for(i=1;i<=n;i++)
    m[i]=i;
 
 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++)
    nr=nr+2*m[i];
 
  fprintf(g,"%lld\n",nr);
  fclose(f);
  fclose(g);
  return 0;}