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 javafx.util.Pair;
public class Solution implements Runnable 
{  
    
    class Pair implements Comparable <Pair>
    {
        long x,y;
        Pair(long x,long y)
        {
            this.x=x;
            this.y=y; 
        }
        public int compareTo(Pair p)
        {
            return Long.compare(x,p.x);
        }
    }
    
    public static void main(String[] args)
    {
        new Thread(null, new Solution(), "rev", 1 << 29).start();
    }

    public void run()
    {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        Task solver = new Task();
        solver.solve(1,in,out);
        out.close();
    }
    
    class Task
    { 
        
        long check(int n)
        {
            long sum=0;
            for(int i=2;i*i<=n;i++)
                if(n%i==0)
                {
                    if(i*i==n)
                        sum+=i;
                    else
                        sum+=(i+n/i);
                }
            return sum;
        }
        
        void solve(int testNumber, InputReader in, PrintWriter out)
        { 
            int []a=new int[100001];
            for(int i=2;i*i<=100000;i++)
            {
                if(a[i]==0)
                    for(int j=2*i;j<=100000;j+=i)
                        a[j]=1;
            }
            long []ans=new long[100001];
            for(int i=2;i<=100000;i++)
                if(a[i]==1)
                    ans[i]=4*check(i);
            int n=in.nextInt();
            long sum=0;
            for(int i=2;i<=n;i++)
                sum+=ans[i];
            out.print(sum);
        }
    }
    
}
  class InputReader 
{
    private InputStream stream;
    private byte[] buf = new byte[8192];
    private int curChar, snumChars;
    private SpaceCharFilter filter;
 
    public InputReader(InputStream stream) 
    {
        this.stream = stream;
    }
 
    public int snext() 
    {
        if(snumChars==-1)
            throw new InputMismatchException();
        if(curChar>=snumChars)
        {
            curChar=0;
            try 
            {
                snumChars = stream.read(buf);                
            } 
            catch(IOException e) 
            {
                throw new InputMismatchException();
            }
            if(snumChars<=0)
                return -1;
        }
        return buf[curChar++];
    }
 
    public int nextInt()
    {
        int c = snext();
        while(isSpaceChar(c))
            c=snext();
        int sgn=1;
        if(c=='-')
        {
            sgn = -1;
            c = snext();
        }
        int res=0;
        do
        {
            if(c<'0' || c>'9')
                throw new InputMismatchException();
            res*=10;
            res+=c-'0';
            c=snext();
            }while(!isSpaceChar(c));
        return res * sgn;
    }
 
    public long nextLong()
    {
        int c = snext();
        while(isSpaceChar(c))
            c=snext();
        int sgn=1;
        if(c=='-')
        {
            sgn=-1;
            c=snext();
        }
        long res=0;
        do{
            if (c<'0' || c>'9')
                throw new InputMismatchException();
            res*=10;
            res+=c-'0';
            c=snext();
        }while (!isSpaceChar(c));
        return res * sgn;
    }
 
    public int[] nextIntArray(int n)
    {
        int a[]=new int[n];
        for(int i=0; i<n; i++)
            a[i]=nextInt();
        return a;
    }
 
    public String nextString()
    {
        int c=snext();
        while(isSpaceChar(c))
            c=snext();
        StringBuilder res=new StringBuilder();
        do{
            res.appendCodePoint(c);
            c = snext();
        }while (!isSpaceChar(c));
        return res.toString();
    }
 
    public boolean isSpaceChar(int c)
    {
        if(filter != null)
            return filter.isSpaceChar(c);
        return c==' ' || c=='\n' || c=='\r' || c=='\t' || c==-1;
    }
 
    public interface SpaceCharFilter
    {
        public boolean isSpaceChar(int ch);
    }
}