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import java.util.*;
import java.lang.*;
import java.lang.reflect.Array;
import java.io.*;
import java.math.*;
import java.text.DecimalFormat;
public class Prac{     
    static class InputReader { 
        private final InputStream stream;
	private final byte[] buf = new byte[8192];
	private int curChar, snumChars;
 	public InputReader(InputStream st) {
            this.stream = st;
	} 
	public int read() {
            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 ni() {
            int c = read();
            while (isSpaceChar(c)) {
               	c = read();
            }
            int sgn = 1;
            if (c == '-') {
		sgn = -1;
		c = read();
            }
            int res = 0;
            do {
		res *= 10;
		res += c - '0';
		c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
	} 
	public long nl() {
            int c = read();
            while (isSpaceChar(c)) {
            c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            long res = 0;
            do {
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
	} 
	public int[] nia(int n) {
            int a[] = new int[n];
            for (int i = 0; i < n; i++) {
		a[i] = ni();
            }
            return a;
	} 
	public String rs() {
            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 String nextLine() {
            int c = read();
            while (isSpaceChar(c))
		c = read();
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            } while (!isEndOfLine(c));
            return res.toString();
        } 
	public boolean isSpaceChar(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
	}
 
	private boolean isEndOfLine(int c) {
            return c == '\n' || c == '\r' || c == -1;
	} 
    }
    static PrintWriter w = new PrintWriter(System.out);
    
    
    
    
    public static void main(String[] args) throws IOException {   
        InputReader sc=new InputReader(System.in);
                long n=sc.ni();
        long ans=0;
        
        for(int i=2;i<=n;i++){
            for(int j=2;j<=n;j++){       
                if(i*j>n){
                    break;
                }
                ans+=(long)j;
            }
        }
        w.println(ans*4);
        w.close();
    }
}



