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

public class Task {

    public static void main(String[] args) throws IOException {

        new Task().go();
    }

    PrintWriter out;
    Reader in;
    BufferedReader br;

    Task() throws IOException {

        try {

            //br = new BufferedReader( new FileReader("input.txt") );
            in = new Reader("input.txt");
            out = new PrintWriter( new BufferedWriter(new FileWriter("output.txt")) );
        }
        catch (Exception e) {

            //br = new BufferedReader( new InputStreamReader( System.in ) );
            in = new Reader();
            out = new PrintWriter( new BufferedWriter(new OutputStreamWriter(System.out)) );
        }
    }

    void go() throws IOException {

        int t = 1;
        while (t > 0) {
            solve();
            //out.println();
            t--;
        }

        out.flush();
        out.close();
    }

    int inf = 2000000000;
    int mod = 1000000007;
    double eps = 0.000000001;

    int n;
    int m;

    int[] a;
    ArrayList<Integer>[] g;
    void solve() throws IOException {

        int n = in.nextInt();
        LinkedList<Integer> q = new LinkedList<>();
        q.add(2);
        boolean[] used = new boolean[n + 1];
        used[2] = true;
        long ans = 0;
        while (!q.isEmpty()) {
            int v = q.poll();
            int cur = 2;
            while (cur * v <= n) {
                ans += cur * 2;
                if (!used[cur * v]) {
                    used[cur * v] = true;
                    q.add(cur * v);
                }
                cur++;
            }

            for (int i = 2; i <= Math.sqrt(v); i++)
                if (v % i == 0 && v / i != 1) {
                    ans += v / i * 2;
                    if (!used[i]) {
                        used[i] = true;
                        q.add(i);
                    }
                    if (i != v / i)
                        ans += i * 2;
                    if (!used[v / i]) {
                        used[v / i] = true;
                        q.add(v / i);
                    }
                }

        }

        out.println(ans);
    }


    class Pair implements Comparable<Pair>{
        int a;
        int b;

        Pair(int a, int b) {
            this.a = a;
            this.b = b;
        }

        public int compareTo(Pair p) {
            if (a > p.a) return 1;
            if (a < p.a) return -1;
            if (b > p.b) return 1;
            if (b < p.b) return -1;
            return 0;
        }
    }

    class Item {

        int a;
        int b;
        int c;

        Item(int a, int b, int c) {
            this.a = a;
            this.b = b;
            this.c = c;
        }

    }

    class Reader {

        BufferedReader  br;
        StringTokenizer tok;

        Reader(String file) throws IOException {
            br = new BufferedReader( new FileReader(file) );
        }

        Reader() throws IOException {
            br = new BufferedReader( new InputStreamReader(System.in) );
        }

        String next() throws IOException {

            while (tok == null || !tok.hasMoreElements())
                tok = new StringTokenizer(br.readLine());
            return tok.nextToken();
        }

        int nextInt() throws NumberFormatException, IOException {
            return Integer.valueOf(next());
        }

        long nextLong() throws NumberFormatException, IOException {
            return Long.valueOf(next());
        }

        double nextDouble() throws NumberFormatException, IOException {
            return Double.valueOf(next());
        }


        String nextLine() throws IOException {
            return br.readLine();
        }

    }

}