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