28237
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 8554
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 39004
 22308
 16054
 71468
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 300
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 90783
 5611
 1000
 69475
 69753
 10
 5
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 8
 36961
 5071
 20
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 92775
 28738
 100000
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 2627
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 3

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import java.util.*;
import java.io.*;
public class Main
{
      static int n;
      static long[] s;
      static ArrayList<Integer> p;
      static void sieve() 
      { 
            int x = (int)1e5;
            p = new ArrayList<Integer>();
            boolean prime[] = new boolean[x+1]; 
            for(int i = 0 ; i < x ; i++) prime[i] = true; 
            for(int p = 2; p*p <= x; p++) 
            {
                  if(prime[p] == true) 
                  {
                        for(int i = p*p; i <= x; i += p) prime[i] = false; 
                  } 
            }
            for(int i = 2; i <= x; i++) 
            { 
                  if(prime[i] == true) p.add(i);
            }
      }
      public static long sigma(int x)
      {
            if(Collections.binarySearch(p,x) >= 0) return (x + 1);
            if(x == 1) return 1;
            if(s[x] > 0) return s[x];
            int k = 0;
            int pow = 0;
            int prime = p.get(0);
            Loop:
            while(true)
            {
                  if(x % prime == 0) 
                  {
                        pow++;
                        x /= prime;
                  }
                  else
                  {
                        if(pow > 0) break Loop;
                        prime = p.get(++k);
                  }
            }
            if(x == 1) return ((long)Math.pow(prime,pow+1) - 1)/((long)prime - 1);
            return (sigma((int)Math.pow(prime,pow)) * sigma(x));
      }
	public static void main (String[] args) throws Exception
	{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		n = Integer.parseInt(br.readLine());
		sieve();
		s = new long[n+1];
		for(int i = 1 ; i <= n ; i++) s[i] = sigma(i);
		for(int i = 2 ; i <= n ; i++) s[i] = s[i]-i-1;
		long sum = 0;
	      for(int i = 2 ; i <= n ; i++) sum += s[i];
	      System.out.println(sum * 4);
	}
}
