#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;      
}