#include <stdio.h>
using namespace std;
bool b[1000000];
int main()
{
    for(int i=2;i<1000000;i++)
    {
        if(b[i]==0)for(int j=2;j<1000000/i;j++)
        {
            b[i*j]=1;
        }
    }
    FILE *fin,*fout;
    fin=fopen("fractii.in","r");
    fout=fopen("fractii.out","w");
    long int n;
    fscanf(fin,"%li",&n);
    long int a[n+1];
    a[1]=1;
    int x=0,temp;
    for(int i=2;i<=n;i++)
    {
        a[i]=a[i-1];
        x=i;
        for(int j=2;j<=i;j++)
        {
            if(b[j]==0)
            {
                if(i%j==0)
                {
                    x*=j-1;
                    x/=j;
                }
            }
        }
        a[i]+=x*2;
    }
    fprintf(fout,"%li",a[n]);
}