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: Wrong Answer)

using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
public class ABC
{


    public static void Main()
    {
        var read = Console.ReadLine().Split().Select(long.Parse).ToArray();
        long N = read[0];
        read = Console.ReadLine().Split().Select(long.Parse).ToArray();
        
        List<long> plusset = new List<long>();
        List<long> minusset = new List<long>();

        for (int i = 0; i < N; i++)
        {
            if (read[i] > 0)
            {
                plusset.Add(read[i]);
            }
            else
            minusset.Add(read[i]);
        }
        plusset.Sort();
        minusset.Sort();
        long[] plus = plusset.ToArray();
        long[] minus = minusset.ToArray();

        if (minus.Length == 0)
        {
            long answer = plus.Sum() - 2 * plus[0];
            long next_target_value = plus[0];

            //kaitou wo kakimasu

            Console.WriteLine(answer);
            for (int i = 0; i < N - 2; i++)
            {
                Console.WriteLine(next_target_value + " " + plus[i + 1]);
                next_target_value -= plus[i + 1];

            }
            Console.WriteLine(plus[N - 1] + " " + next_target_value);
        }
        else if (plus.Length == 0)
        {
            long answer = minus.Sum() - 2 * minus[0];
            long next_target_value = minus[0];

            //kaitou wo kakimasu

            Console.WriteLine(answer);
            for (int i = 0; i < N - 2; i++)
            {
                Console.WriteLine(next_target_value + " " + minus[i + 1]);
                next_target_value -= minus[i + 1];

            }
            Console.WriteLine(minus[N - 1] + " " + next_target_value);
        }

        else
        {
            solver(plus, minus);

        }




    }


    public static void solver(long[] plus,long[] minus)
    {
        Console.WriteLine(plus.Sum() - minus.Sum());
        long make_big = plus[0];

        for (int m = 0; m < minus.Length-1; m++)
        {
            Console.WriteLine(make_big + " " + minus[m]);
            make_big -= minus[m];

        }
        long make_small = minus.Last();
        for (int p = 1; p < plus.Length; p++)
        {
            Console.WriteLine(make_small + " " + plus[p]);
            make_small -= plus[p];

        }
        Console.WriteLine(make_big + " " + make_small);



    }
}