import java.io.*;
import java.util.*;

import java.math.*;
import java.lang.*;
 
public class Main implements Runnable {
    
    InputReader sc = new InputReader(System.in);
    PrintWriter out = new PrintWriter(System.out);

    static int MAX = 10000001; 
	static int factor[]; 

	static void generatePrimeFactors() 
	{ 
		factor[1] = 1; 
		for (int i = 2; i < MAX; i++) 
			factor[i] = i; 

		for (int i = 4; i < MAX; i += 2) 
			factor[i] = 2; 

		for (int i = 3; i * i < MAX; i++) { 
			if (factor[i] == i) { 
				for (int j = i * i; j < MAX; j += i) { 
					if (factor[j] == j) 
						factor[j] = i; 
				} 
			} 
		} 
	} 

	static int calculateNoOFactors(int n) 
	{ 
		if (n == 1) 
			return 1; 

		int ans = 1; 
		int dup = factor[n]; 
		int c = 1; 
		int j = n / factor[n]; 

		while (j != 1) { 
			if (factor[j] == dup) 
				c += 1; 
			else { 
				dup = factor[j]; 
				ans = ans * (c + 1); 
				c = 1; 
			} 

			j = j / factor[j]; 
		} 

		ans = ans * (c + 1); 

		return ans; 
	} 

    public void run() {
       
        factor = new int[MAX]; 
		factor[0] = 0; 

		generatePrimeFactors(); 

        int n=sc.nextInt();
        long ans=0;
        for(int i=1;i<=n;i++)
        {
            ans+=i*(long)calculateNoOFactors(i);
        }
        out.println(ans);
        out.close();
    }

//========================================================

	static class Pair
	{
		int a,b;
		Pair(int aa,int bb)
		{
			a=aa;
			b=bb;
		}
	}
	
	static void sa(int a[],InputReader sc)
	{
		for(int i=0;i<a.length;i++)
		{
			a[i]=sc.nextInt();
		}
		
	}

    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 Main(),"Main",1<<27).start();
    }
}


Measured memory_bytes: 72472