You are given a positive integer n greater or equal to 2. For every pair of integers a and b (2 ≤ |a|, |b| ≤ n), you can transform a into b if and only if there exists an integer x such that 1 < |x| and (a ⋅ x = b or b ⋅ x = a), where |x| denotes the absolute value of x.

After such a transformation, your score increases by |x| points and you are not allowed to transform a into b nor b into a anymore.

Initially, you have a score of 0. You can start at any integer and transform it as many times as you like. What is the maximum score you can achieve?

Input

A single line contains a single integer n (2 ≤ n ≤ 100 000) — the given integer described above.

Output

Print an only integer — the maximum score that can be achieved with the transformations. If it is not possible to perform even a single transformation for all possible starting integers, print 0.

Examples

Input

4


Output

8

Input

6


Output

28

Input

2


Output

0

Note

In the first example, the transformations are 2 → 4 → (-2) → (-4) → 2.

In the third example, it is impossible to perform even a single transformation.
import java.util.*;
import java.io.*;
import java.math.*;
/*
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
StringTokenizer st = new StringTokenizer(br.readLine());
Integer.parseInt(st.nextToken());
Long.parseLong(st.nextToken());
Scanner sc = new Scanner(System.in);


*/

public class Waw{
    
    public static long countDivisors(int n){
        long nb = 0;
        for(int i=2;i<=Math.sqrt(n);i++){
            if(n%i==0){
                if(n/i==i) nb += (long) (i*4);
                else{
                    nb += (long) (i*4);
                    nb += (long) ((n/i)*4);
                }
            }
        }
        
        return nb;
    }
    
    public static void main(String[] args){
        
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        long nb = 0;
        for(int i=n;i>=2;i--){
            nb += countDivisors(i);
        }
        
        System.out.println(nb);
        
        
    
    }
}