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;
using System.Text;
using static System.Console;
using static System.Math;

namespace AtTest.diverta2019_2
{
    class C
    {
        static void Main(string[] args)
        {
            Method(args);
        }

        static void Method(string[] args)
        {
            int n = ReadInt();
            long[] array = ReadLongs();
            /*long[] sorted = array.OrderBy(a => a).ToArray();
            long m = 0;
            for(int i = 0; i < n; i++)
            {
                if (i < n - 1 && sorted[i] < 0) m += -sorted[i];
                else m += sorted[i];
            }*/
            int maxIndex = 0;
            int minIndex = 0;
            for(int i = 0; i < n; i++)
            {
                if (array[maxIndex] < array[i]) maxIndex = i;
                if (array[minIndex] >= array[i]) minIndex = i;
            }
            long m = 0;
            for(int i = 0; i < n; i++)
            {
                if (i == minIndex || i == maxIndex) continue;
                m += Abs(array[i]);
            }
            m += array[maxIndex];
            m -= array[minIndex];

            var sw = new System.IO.StreamWriter(OpenStandardOutput()) { AutoFlush = false };
            SetOut(sw);

            WriteLine(m);
            for(int i = 0; i < n; i++)
            {
                if (i == minIndex || i == maxIndex) continue;

                if (array[i] < 0)
                {
                    WriteLine(array[maxIndex] + " " + array[i]);
                    array[maxIndex] -= array[i];
                }
                else
                {
                    WriteLine(array[minIndex] + " " + array[i]);
                    array[minIndex] -= array[i];
                }
            }
            WriteLine(array[maxIndex] + " " + array[minIndex]);

            Out.Flush();
        }

        private static string Read() { return ReadLine(); }
        private static char[] ReadChars() { return Array.ConvertAll(Read().Split(), a => a[0]); }
        private static int ReadInt() { return int.Parse(Read()); }
        private static long ReadLong() { return long.Parse(Read()); }
        private static double ReadDouble() { return double.Parse(Read()); }
        private static int[] ReadInts() { return Array.ConvertAll(Read().Split(), int.Parse); }
        private static long[] ReadLongs() { return Array.ConvertAll(Read().Split(), long.Parse); }
        private static double[] ReadDoubles() { return Array.ConvertAll(Read().Split(), double.Parse); }
    }
}