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.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.InputMismatchException;
import java.util.TreeMap;
import java.util.TreeSet;
				 
				 
				 
				 
				 
				public class Solution1 implements Runnable
				{
				    static final long MOD = 1000000007;
				    static class InputReader
				    {
				        private InputStream stream;
				        private byte[] buf = new byte[1024];
				        private int curChar;
				        private int numChars;
				        private SpaceCharFilter filter;
				        private BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
				 
				        public InputReader(InputStream stream)
				        {
				            this.stream = stream;
				        }
				        
				        public int read()
				        {
				            if (numChars==-1) 
				                throw new InputMismatchException();
				            
				            if (curChar >= numChars)
				            {
				                curChar = 0;
				                try 
				                {
				                    numChars = stream.read(buf);
				                }
				                catch (IOException e)
				                {
				                    throw new InputMismatchException();
				                }
				                
				                if(numChars <= 0)                
				                    return -1;
				            }
				            return buf[curChar++];
				        }
				     
				        public String nextLine()
				        {
				            String str = "";
				            try
				            {
				                str = br.readLine();
				            }
				            catch (IOException e)
				            {
				                e.printStackTrace();
				            }
				            return str;
				        }
				        public int nextInt()
				        {
				            int c = read();
				            
				            while(isSpaceChar(c)) 
				                c = read();
				            
				            int sgn = 1;
				            
				            if (c == '-') 
				            {
				                sgn = -1;
				                c = read();
				            }
				            
				            int res = 0;
				            do 
				            {
				                if(c<'0'||c>'9') 
				                    throw new InputMismatchException();
				                res *= 10;
				                res += c - '0';
				                c = read();
				            }
				            while (!isSpaceChar(c)); 
				            
				            return res * sgn;
				        }
				        
				        public long nextLong() 
				        {
				            int c = read();
				            while (isSpaceChar(c))
				                c = read();
				            int sgn = 1;
				            if (c == '-') 
				            {
				                sgn = -1;
				                c = read();
				            }
				            long res = 0;
				            
				            do 
				            {
				                if (c < '0' || c > '9')
				                    throw new InputMismatchException();
				                res *= 10;
				                res += c - '0';
				                c = read();
				            }
				            while (!isSpaceChar(c));
				                return res * sgn;
				        }
				        
				        public double nextDouble() 
				        {
				            int c = read();
				            while (isSpaceChar(c))
				                c = read();
				            int sgn = 1;
				            if (c == '-') 
				            {
				                sgn = -1;
				                c = read();
				            }
				            double res = 0;
				            while (!isSpaceChar(c) && c != '.') 
				            {
				                if (c == 'e' || c == 'E')
				                    return res * Math.pow(10, nextInt());
				                if (c < '0' || c > '9')
				                    throw new InputMismatchException();
				                res *= 10;
				                res += c - '0';
				                c = read();
				            }
				            if (c == '.') 
				            {
				                c = read();
				                double m = 1;
				                while (!isSpaceChar(c)) 
				                {
				                    if (c == 'e' || c == 'E')
				                        return res * Math.pow(10, nextInt());
				                    if (c < '0' || c > '9')
				                        throw new InputMismatchException();
				                    m /= 10;
				                    res += (c - '0') * m;
				                    c = read();
				                }
				            }
				            return res * sgn;
				        }
				        
				        public String readString() 
				        {
				            int c = read();
				            while (isSpaceChar(c))
				                c = read();
				            StringBuilder res = new StringBuilder();
				            do 
				            {
				                res.appendCodePoint(c);
				                c = read();
				            } 
				            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 String next() 
				        {
				            return readString();
				        }
				        
				        public interface SpaceCharFilter 
				        {
				            public boolean isSpaceChar(int ch);
				        }
				    }
				     
				    public static void main(String args[]) throws Exception
				    {
				        new Thread(null, new Solution1(),"Solution",1<<26).start();
				    }   
				    static long gcd(long a, long b) 
				    { 
				      if (b == 0) 
				        return a; 
				      return gcd(b, a % b);  
				    } 
				    static long lcm(long a,long b) {
				    	return (a*b)/gcd(a,b);
				    }
				    ArrayList<Integer> adj[];
				    public void run() 
				    {
				    	InputReader sc = new InputReader(System.in);
						PrintWriter w = new PrintWriter(System.out);
						int n = sc.nextInt();
						long ans = 0;
						for(int i= 2;i <= n;i++) {
							long temp = n/i;
							long temp1 = (temp * (temp + 1)/2 - 1) * 4;
							ans += temp1;
						}
						w.println(ans);
						w.close();
				    }
				    long[] fact = new long[100005];	
				    long nCr(int n,int r){ 
				    	long tmp1 = (fact[r] * fact[n-r]) % MOD;
				    	tmp1 = power(tmp1,MOD-2,MOD);
				    	long tmp2 = (fact[n] * tmp1) % MOD;
				    	return tmp2;
	 			    }
				    static long power(long a,long b,long mod) {
						long ans = 1;
						a = a % mod;
						while(b != 0) {
							if(b % 2 == 1) {
								ans = (ans * a) % mod;
							}
							a = (a * a) % mod;
							b = b/2;
						}
						return ans;
					}
				   void pre() {
					   fact[0] = 1;
					   for(int i = 1;i < 100005;i++) {
						   fact[i] = (fact[i-1] * i) % MOD;
					   }
				   }
				    class Pair implements Comparable<Pair>{
				        int a;
				        int b;
				        Pair(int a,int b){
				            this.b = b;
				            this.a = a;
				            
				        }
				        public boolean equals(Object o) {
				            Pair p = (Pair)o;
				            return this.a == p.a && this.b == this.b;
				        }
				        public int hashCode(){
				            return Long.hashCode(a)*27 + Long.hashCode(b)*31;
				        }
				        public int compareTo(Pair p) {
				            return Long.compare(this.a,p.a);
				        }
				    }
				    
				}