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.Collections.Generic;
using System.Linq;

class C
{
	static void Main()
	{
		var n = int.Parse(Console.ReadLine());
		var a = Console.ReadLine().Split().Select(int.Parse).OrderBy(x => x).ToArray();

		var M = 0;
		var l = new List<string>();
		if (a[0] >= 0)
		{
			M = a[0];
			for (int i = 1; i < n - 1; i++)
			{
				l.Add($"{M} {a[i]}");
				M -= a[i];
			}
			l.Add($"{a[n - 1]} {M}");
			M = a[n - 1] - M;
		}
		else if (a[n - 1] <= 0)
		{
			M = a[n - 1];
			for (int i = 0; i < n - 1; i++)
			{
				l.Add($"{M} {a[i]}");
				M -= a[i];
			}
		}
		else
		{
			M = a[0];
			int i = n - 2;
			for (; a[i] > 0; i--)
			{
				l.Add($"{M} {a[i]}");
				M -= a[i];
			}
			l.Add($"{a[n - 1]} {M}");
			M = a[n - 1] - M;
			for (; i > 0; i--)
			{
				l.Add($"{M} {a[i]}");
				M -= a[i];
			}
		}
		Console.WriteLine(M);
		foreach (var item in l) Console.WriteLine(item);
	}
}