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