#include<stdio.h>         
long long unsigned n,i,j,s,a[2000000],k;         
int main()         
{         
FILE *f=fopen("fractii.in","r"), *g=fopen("fractii.out","w");         
fscanf(f,"%llu",&n);         
for(i=2;i<=n;++i)         
    if (a[i]==0)         
            for (j=i*2;j<=n;j=j+i)         
                    if (j%i==0)         
                           {   if (a[j]==0)         
                             a[j]=j;         
                              a[j]=a[j]-a[j]/i;         
                              }         
        
        
for (i=1;i<=n;++i)         
    if (a[i]==0)         
       s=s+i-1;         
       else s=s+a[i];         
fprintf(g,"%llu",s*2+1);         
return 0;         
}