#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;   
}