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
fscanf(STDIN, "%d", $N);
  $numArray = explode(" ", trim(fgets(STDIN)));
$str= array();
rsort($numArray);

for($i=1;isset($numArray[1])&&$i<$N&&$numArray[1]>0;$i++){
    $str[]=$numArray[$N-$i]." ".$numArray[1];
    $numArray[$N-$i]=$numArray[$N-$i]-$numArray[1];
    array_splice($numArray, 1, 1);
}

sort($numArray);
$M=count($numArray);
for($j=1;$j<$M;$j++){
  $str[]= $numArray[$j]." ".$numArray[0];
  $numArray[0]=$numArray[$j]-$numArray[0];
}

  echo ($numArray[0])."\n";
foreach($str as $s){
  echo ($s)."\n";
}
 
?>