Problem:
Score : 500 points

Problem Statement

There are N integers, A_1, A_2, ..., A_N, written on a blackboard.

We will repeat the following operation N-1 times so that we have only one integer on the blackboard.

Choose two integers x and y on the blackboard and erase these two integers. Then, write a new integer x-y.

Find the maximum possible value of the final integer on the blackboard and a sequence of operations that maximizes the final integer.

Constraints

2 \leq N \leq 10^5

-10^4 \leq A_i \leq 10^4

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N
A_1 A_2 ... A_N

Output

Print the maximum possible value M of the final integer on the blackboard, and a sequence of operations x_i, y_i that maximizes the final integer, in the format below.

Here x_i and y_i represent the integers x and y chosen in the i-th operation, respectively.

If there are multiple sequences of operations that maximize the final integer, any of them will be accepted.

M
x_1 y_1
:
x_{N-1} y_{N-1}

Sample Input 1

3
1 -1 2

Sample Output 1

4
-1 1
2 -2

If we choose x = -1 and y = 1 in the first operation, the set of integers written on the blackboard becomes (-2, 2).

Then, if we choose x = 2 and y = -2 in the second operation, the set of integers written on the blackboard becomes (4).

In this case, we have 4 as the final integer. We cannot end with a greater integer, so the answer is 4.

Sample Input 2

3
1 1 1

Sample Output 2

1
1 1
1 0

Solution in PHP7 (7.0.15) (judge verdict: Wrong Answer)

<?php
$n = (int)trim(fgets(STDIN));

$input = explode(' ', trim(fgets(STDIN)));
$as = [];
foreach ($input as $v) {
	$as[] = (int)$v;
}
sort($as);

if ($n === 2) {
	echo ($as[1] - $as[0]) . PHP_EOL;
	echo $as[1] . ' ' . $as[0];
	exit();
}
$tmp = $as[0] - $as[1];
$result = [];
$result[] = $as[0] . ' ' . $as[1];
for ($i=2; $i < $n; $i++) { 
	if ($i === $n-1) {
		$result[] = $as[$i] . ' ' . $tmp;
		$tmp = $as[$i] - $tmp;
	}else{
		$tmp = $tmp - $as[$i];
		$result[] = $tmp . ' ' . $as[$i];
	}
}
echo $tmp . PHP_EOL;
echo implode(PHP_EOL, $result);