#include<stdio.h>
long long nr=0;
int i,j,n,v[1000001];
int main()
{
 freopen("fractii.in","r",stdin);
 freopen("fractii.out","w",stdout);
 scanf("%d",&n);
 for(i=2;i<=n;i++)
   v[i]=i-1;
for(i=2;i<=n;i++)
  {
   nr=nr+v[i];
   for(j=i+i;j<=n;j=j+i)
   v[j]=v[j]-v[i];
  }
 nr=nr*2+1;
 printf("%lld",nr);
 return 0;
}