28237
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 5611
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 8
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 3

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//package Div2_520;

import java.util.Scanner;

public class D {
    static int n;
    static int snm[][];

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        n = in.nextInt() + 1;
        marked = new long[n];
        snm = new int[n][2];
        for (int i = 0; i < n; i++) {
            snm[i][0] = i;
        }
        func();
        long mas[] = new long[n];
        for (int i = 2; i < n; i++) {
            mas[snm[i][0]] += marked[i];
        }
        long ans = 0;
        for (int i = 0; i < n; i++) {
            if (mas[i] > ans) ans = mas[i];
        }
        System.out.println(ans);
    }

    private static void func() {
        for (int i = 0; i < n; i++) {
            marked[i] = -1;
        }
        for (int i = 2; i < n; i++) {
            if (marked[i] == -1) {
                fu(i);
            }
        }
    }

    private static void fu(int x) {
        marked[x] = 0;
        for (long i = 2; i * x < n; i++) {
            marked[x] += 4 * i;
            int y = pred(x);
            int z = pred((int) i * x);
            if (y != z) {
                if (snm[y][1] == snm[z][1]) {
                    snm[y][1]++;
                    snm[z][0] = y;
                } else if (snm[y][1] > snm[z][1]) {
                    snm[z][0] = y;
                } else {
                    snm[y][0] = z;
                }
            }
        }
    }

    private static int pred(int l) {
        while (snm[l][0] != l) {
            l = snm[l][0];
        }
        return l;
    }

    static long marked[];

}
