## IPSC 2004

## Problem B – Bishops

Yesterday was Sam's birthday. The most interesting gift was definitely
the chessboard. Sam quickly learned the rules of chess and defeated
his father, all his friends, his little sister, and now no one wants
to play with him any more.

So he decided to play with another birthday gift – a Book of Math
Problems for Young Mathematicians. He opened the book somewhere in the
middle and read the following problem: "How many knights can be placed
on a chessboard without threatening each other?" After a while he
realized that this was trivial and moved on to the next problem: "How
many bishops can be placed on a chessboard without threatening each
other?". Sam is in trouble here. He is not able to solve this problem
and needs your help.

### Task Specification

Sam's chessboard has size **N×N**. A bishop can move to any distance in
any of the four diagonal directions. A bishop threatens another bishop
if it can move to the other bishop's position. Your task is to
compute the maximum number of bishops that can be placed on a
chessboard in such a way that no two bishops threaten each other.

### Input specification

The input file consists of several lines. The line number i contains
a single number representing the size of the **i**-th chessboard.

### Output specification

The output file should contain the same number of lines as the input
file. The **i**-th line should contain one number – the maximum number
of bishops that can be placed on **i**-th chessboard without threatening
each other.

### Example

**Input file:**
2
3

**Output file:**
2
4