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.BigInteger;
import java.util.regex.*;

public class Codeforces{
	
	static class MyScanner{
		BufferedReader br;
		StringTokenizer st;
		
		MyScanner(FileReader fileReader){
			br = new BufferedReader(fileReader);
		}
		
		MyScanner(){
			br = new BufferedReader(new InputStreamReader(System.in));
		}
		
		String nn(){
			while(st == null || !st.hasMoreElements()){
				try{
					st = new StringTokenizer(br.readLine());
				}catch(IOException e){
					e.printStackTrace();
				}
			}
			return st.nextToken();
		}
		
		String nextLine(){
			String s = "";
			try{
				s = br.readLine();
			}catch(IOException e){
				e.printStackTrace();
			}
			return s;
		}
		
		int ni(){
			return Integer.parseInt(nn());
		}
		
		long nl(){
			return Long.parseLong(nn());
		}
		
		double nd(){
			return Double.parseDouble(nn());
		}
	}
	
	private static PrintWriter out;
	
	public static void main(String[] args) throws FileNotFoundException{
		
		// Input from file
		// File inputFile = new File("JavaFile.txt");
		// File outputFile = new File("JavaOutputFile.txt");
		// FileReader fileReader = new FileReader(inputFile);
		// Here it ends
			
		MyScanner sc = new MyScanner();
		// MyScanner sc = new MyScanner(fileReader);
		
		out = new PrintWriter(new BufferedOutputStream(System.out)); // Output to console
		// out = new PrintWriter(new PrintStream(outputFile)); // Output to file
		
		int n = sc.ni();
		long ans = 0;
		
		for(int i = 2; i <= n; i++){
			ans += 4 * i * (n / i - 1);
		}
		
		out.println(ans);
		
		out.close();
	}
}