//infoarena
#include<cstdio>
using namespace std;
FILE *f=fopen("fractii.in","r");
FILE *g=fopen("fractii.out","w");
int  n,i,j,a[1000000];
long long int nr;
int main()
{
  fscanf(f,"%d",&n);
  for(i=0;i<=n-2;i++)
    a[i]=i+1;
  for(i=0;i<=n-2;i++)
  {
    nr+=a[i];
    for(j=2*(i+2);j<=n-2;j+=i)
      a[j]-=a[i];
  }
  fprintf(g,"%lld",2*nr+1);
  return 0;
}