#include <stdio.h>
long long a[999999];
int main()
{
	long i,j,n;
	long long k=0;
	freopen("fractii.in","r",stdin);
	freopen("fractii.out","w",stdout);
	for (i=2;i<=n;i++)
		a[i]=i;
	for (i=2;i<=n;i++)
	{
		if(a[i]==i){
			for(j=i;j<=n;j+=i){
				a[j]=a[j]/i;
				a[j]=a[j]*(i-1);
			}
		}
		k=k+2*a[i];
	}
k=k-1;
printf("%lld",k);
return 0;
}