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

public class Main {

    void solve() throws IOException {
        int n = readInt();
        long r =0;
        for(int i=2;i<=n;i++){
            long t = n/i;
            r += 4L*(t*(t+1)/2 -1);
        }
        out.print(r);

    }


    void init() throws FileNotFoundException {
        try {
            in = new BufferedReader(new FileReader("input.txt"));
            out = new PrintWriter("output.txt");
        } catch (Exception e) {
            in = new BufferedReader(new InputStreamReader(System.in));
            out = new PrintWriter(System.out);
        }
        tok = new
                StringTokenizer("");
    }

    int minInt(int... values) {
        int min = Integer.MAX_VALUE;
        for (int value : values) {
            min = Math.min(min, value);
        }
        return min;
    }

    int maxInt(int... values) {
        int max = Integer.MIN_VALUE;
        for (int value : values) {
            max = Math.max(max, value);
        }
        return max;
    }

    long minLong(long... values) {
        long min = Long.MAX_VALUE;
        for (long value : values) {
            min = Math.min(min, value);
        }
        return min;
    }

    long maxLong(long... values) {
        long max = Long.MIN_VALUE;
        for (long value : values) {
            max = Math.max(max, value);
        }
        return max;
    }

    boolean checkIndex(int index, int size) {
        return (0 <= index && index < size);
    }

    int abs(int a) {
        if (a < 0) return -a;
        return a;
    }

    long abs(long a) {
        if (a < 0) return -a;
        return a;
    }

    int gcd(int a, int b) {
        int tmp = 0;
        while (b != 0) {
            tmp = a;
            a = b;
            b = tmp % a;
        }
        return a;
    }

    long gcd(long a, long b) {
        long tmp = 0;
        while (b != 0) {
            tmp = a;
            a = b;
            b = tmp % a;
        }
        return a;
    }

    public static void main(String[] args) {
        new Main().run();
    }

    BufferedReader in;
    PrintWriter out;
    StringTokenizer tok;


    void run() {
        try {
            long timeStart = System.currentTimeMillis();
            init();
            solve();
            out.close();
            long timeEnd = System.currentTimeMillis();
            System.err.println("time = " + (timeEnd - timeStart) + " compiled");
        } catch (Exception e) {
            e.printStackTrace();
            System.exit(-1);
        }


    }

    String readLine() throws IOException {
        return in.readLine();
    }

    String delimiter = " ";

    String readString() throws IOException {
        while (!tok.hasMoreTokens()) {
            String nextLine = readLine();
            if (null == nextLine)
                return null;

            tok = new StringTokenizer(nextLine);
        }

        return tok.nextToken(delimiter);
    }

    int[] readIntArray(int b) {
        int a[] = new int[b];
        for (int i = 0; i < b; i++) {
            try {
                a[i] = readInt();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return a;
    }

    double readDouble() throws IOException {
        return Double.parseDouble(readString());
    }

    int readInt() throws IOException {
        return Integer.parseInt(readString());
    }

    long readLong() throws IOException {
        return Long.parseLong(readString());
    }

}