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.io.*;
import java.math.BigInteger;
import java.util.*;
                                 
public class Main {
                             
    static Scanner in;
         
//  static StreamTokenizer in;
//  static int nextInt() throws IOException {
//      in.nextToken();
//      return (int)in.nval;    
//  }
    static Random rand = new Random();
    static long gcd(long a, long c) {
        BigInteger q = BigInteger.valueOf(a);
        BigInteger w = BigInteger.valueOf(c);
        q = q.gcd(w);
        return q.longValue();
    }
    static int[] w, d;
   
    public static void main(String args[]) throws IOException {
    	
//      in = new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
        in = new Scanner(System.in);         
        PrintWriter out = new PrintWriter(System.out);
        int n = in.nextInt();
        long[] pref = new long[n];
       
        pref[0] = 0;
        pref[1] = 0;
        int a = 8;
        for(int i =2;i<n;i++) {
        	pref[i] = a + pref[i-1];
        	a+=4;
        }
//        System.out.println(pref[n-1]);
        long ans = 0;
        long max = 0;
        for(int i= 2;i<n;i++) {
        	ans+= pref[n/i];
//        	System.out.println(pref[n/i]);
//        	max = Math.max(ans, max);
        }
        System.out.println(ans);
        out.close();
    }
}
                                 
class Pair implements Comparable{
	int a;
    int b;

    public Pair() {
        this.a = 0;
        this.b = 0;
    }
    public Pair(int a, int b) {
        this.a = a;
        this.b = b;

    }
    public int compareTo(Object arg0) {
        if(Integer.compare(this.a, ((Pair) arg0).a) == 0) return Integer.compare(this.b, ((Pair) arg0).b);
            return Integer.compare(this.a, ((Pair) arg0).a);
    }
}