#include<stdio.h>
FILE *f,*g;
long long max=0;
int i,j,n,nr[1000001];
int main()
{f=fopen("fractii.in","rt");
 g=fopen("fractii.out","wt");
 fscanf(f,"%d",&n);
 for(i=2;i<=n;i++) nr[i]=i-1;
 for(i=2;i<=n;i++)
              {max+=nr[i];
               for(j=i+i;j<=n;j=j+i)
                nr[j]-=nr[i];
               }
 max=max*2+1;
 fprintf(g,"%lld",max);
 return 0;
}