You are given a positive integer n greater or equal to 2. For every pair of integers a and b (2 ≤ |a|, |b| ≤ n), you can transform a into b if and only if there exists an integer x such that 1 < |x| and (a ⋅ x = b or b ⋅ x = a), where |x| denotes the absolute value of x.

After such a transformation, your score increases by |x| points and you are not allowed to transform a into b nor b into a anymore.

Initially, you have a score of 0. You can start at any integer and transform it as many times as you like. What is the maximum score you can achieve?

Input

A single line contains a single integer n (2 ≤ n ≤ 100 000) — the given integer described above.

Output

Print an only integer — the maximum score that can be achieved with the transformations. If it is not possible to perform even a single transformation for all possible starting integers, print 0.

Examples

Input

4


Output

8

Input

6


Output

28

Input

2


Output

0

Note

In the first example, the transformations are 2 → 4 → (-2) → (-4) → 2.

In the third example, it is impossible to perform even a single transformation.
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.List;
import java.util.Random;
import java.util.StringTokenizer;

public class Main implements Runnable {

	int sz[];
	int id[];
	List<Integer> edges[];
	long tree[];

	private void solve() throws IOException {
		int n = nextInt();
		long ans = 0;
		for (int i = 2; i < n; ++i) {
			int tmp = n / i;
			ans += 4 * (tmp * 1L * (tmp + 1) / 2 - 1);
		}
		pw.println(ans);
	}

	void test() throws IOException {
		Random rnd = new Random();
		for (int i = 0; i < 5; ++i) {
			int n = rnd.nextInt(10) + 1;
			int a[] = new int[n];
			System.err.println(n);
			for (int j = 0; j < n; ++j) {
				a[j] = rnd.nextInt(20) + 1;
				System.err.print(a[j] + " ");
			}
//			solve(n, a);
			System.err.println();
		}
	}

	BufferedReader br;
	StringTokenizer st;
	PrintWriter pw;

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

	public void run() {
		try {
			br = new BufferedReader(new InputStreamReader(System.in), 32768);
			pw = new PrintWriter(System.out);
			st = null;
			solve();
			pw.flush();
			pw.close();
			br.close();
		} catch (IOException e) {
			e.printStackTrace();
			System.exit(1);
		}
	}

	int nextInt() throws IOException {
		return Integer.parseInt(next());
	}

	long nextLong() throws IOException {
		return Long.parseLong(next());
	}

	double nextDouble() throws IOException {
		return Double.parseDouble(next());
	}

	String next() throws IOException {
		while (st == null || !st.hasMoreTokens()) {
			st = new StringTokenizer(br.readLine());
		}
		return st.nextToken();
	}
}
