#include <iostream>
#include <cstdio>

using namespace std;
int n,i,j,a[100000000];
long long s;

int main()
{
     freopen("fractii.in","r",stdin);
     freopen("fractii.out","w",stdout);
     scanf("%d",&n);
     for(i=1;i<=n;i++)
                      a[i]=i-1;
     for(i=2;i<=n;i++)
                     { for(j=2*i;j<=n;j+=i)
                          a[j]=a[j]-a[i];          
                          s=s+2*a[i];
                     }                                       
     printf("%d",s);
     return 0;
     
}