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 C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Linq;//リストの使用
using System.Collections.Generic;
using System.Text;//テキストの高速出力に必要
class Program
{
	static void Main()
	{
		int n = int.Parse(Console.ReadLine());
		long[] nums = Array.ConvertAll(Console.ReadLine().Split(' '),long.Parse);
    Array.Sort(nums);
    long answer = 0;
    for(int i = 1; i < n-1; i++)
    {
      answer += Math.Abs(nums[i]);
    }
    if(nums[0] > 0 || nums[n-1] < 0)
    {
      answer -= nums[0];
      answer += nums[n-1];
    }else
    {
      answer += Math.Abs(nums[0]) + Math.Abs(nums[n-1]);
    }
		Console.WriteLine(answer);

    long minusCount = 0;
    long minusMemo = nums[n-1];
    long plusMemo = nums[0];
    
    for(int i = 1; i < n-1; i++)
    {
      if(nums[i] >= 0) break;
      minusCount++;
    }

    for(int i = 0; i < minusCount; i++)
    {
      Console.WriteLine(minusMemo+" "+nums[i+1]);
      minusMemo -= nums[i+1];
    }
    for(int i = 0; i < n-2-minusCount; i++)
    {
      Console.WriteLine(plusMemo+" "+nums[minusCount+1+i]);
      plusMemo -= nums[minusCount+1+i];
    }
    Console.WriteLine(minusMemo+" "+plusMemo);
	}
}