#include <stdio.h>
#include <stdlib.h>
long *p,*s,i,j,n;
double sum=0;

int main(char *argv[],int argc)
{
	
	freopen("fractii.in","r",stdin);
	scanf("%d",&n);
	fclose(stdin);
	s=new long[n];
    p=new long[n];
   	for(i=0;i<=n;i++)
	{
		s[i]=0;
		p[i]=i;
	}
	if (n==1) sum=1;
	else{
	for(j=2;j<=n;j++)
		if(s[j]==0)
		{
			for(i=j;i<=n;i+=j)
			{
				s[i]=1;
				p[i]=((p[i])/j)*(j-1);
			}
		}
	for(i=2;i<=n;i++)
		sum+=(p[i]);
	sum=sum*2+1;}
	freopen("fractii.out","w",stdout);
	printf("%.0lf",sum);
	fclose(stdout);
    return 0;
}