D. Fun with Integers
time limit per test
2 seconds
memory limit per test
256 megabytes
input
standard input
output
standard output

You are given a positive integer $n$ greater or equal to $2$. For every pair of integers $a$ and $b$ ($2 \le |a|, |b| \le n$), you can transform $a$ into $b$ if and only if there exists an integer $x$ such that $1 < |x|$ and ($a \cdot x = b$ or $b \cdot x = a$), 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 $n$ ($2 \le n \le 100\,000$) — 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 $2 \rightarrow 4 \rightarrow (-2) \rightarrow (-4) \rightarrow 2$.

In the third example, it is impossible to perform even a single transformation.