Multiplication Table

• Time limit: 1.00 s
• Memory limit: 512 MB

Find the middle element when the numbers in an $n \times n$ multiplication table are sorted in increasing order. It is assumed that $n$ is odd.

For example, the $3 \times 3$ multiplication table is as follows:
\[
\begin{matrix}
1 & 2 & 3 \\
2 & 4 & 6 \\
3 & 6 & 9 \\
\end{matrix}
\]
The numbers in increasing order are $[1,2,2,3,3,4,6,6,9]$, so the answer is $3$.

Input

The only input line has an integer $n$.

Output

Print one integer: the answer to the task.

Constraints

• $1 \le n < 10^6$
  

Example

Input:
3

Output:
3