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;//list用
using System.Text;//StringBuilder用
using System.Collections;
using System.Linq;
class Program
{
    static List<int> s=new List<int>();
      static List<int> p=new List<int>();
        static List<int> m=new List<int>();
    static decimal result;
static Hashtable ht=new Hashtable();
static int N,M;
    static void Main()
    {
Read1();
      Read2();
//合計値が最大になればＯＫ。
//マイナスはそのまま，プラスは一度他のマイナスから引いてやってからベースに結果に引き渡す。      
//
      s.Sort();
for(int i=0;i<N;i++){
if(s[i]>=0){p.Add(s[i]);}else{m.Add(s[i]);}
}
if(m.Count==0){for(int i=1;i<p.Count;i++){result+=p[i];}result-=p[0];}      
else if(p.Count==0){for(int i=0;i<m.Count-1;i++){result-=m[i];}result+=m[m.Count-1];}                  
else{int pr=p[0];
     int mr=m[0];
     for(int i=1;i<p.Count;i++){mr-=p[i];}
      for(int i=1;i<m.Count;i++){pr-=m[i];}    
     result=pr-mr;
    }
                    Console.WriteLine(result.ToString());
      
if(m.Count==0){
  result=p[0];
    for(int i=1;i<p.Count-1;i++){
                      Console.WriteLine(result.ToString() + " " + p[i]);
result-=p[i];}
  Console.WriteLine(p[p.Count-1] + " " + result.ToString());
  }      
else if(p.Count==0){
  result=m[m.Count-1];
  for(int i=0;i<m.Count-1;i++){
  Console.WriteLine(result.ToString() + " " + m[i]);
    result-=m[i];
  }}                  
else{int pr=p[0];
     int mr=m[0];
     for(int i=1;i<p.Count;i++){
  Console.WriteLine(mr.ToString() + " " + p[i]);       
       mr-=p[i];}
      for(int i=1;i<m.Count;i++){
  Console.WriteLine(pr.ToString() + " " + m[i]);        
        pr-=m[i];}
   Console.WriteLine(pr + " " + mr);    
     result=pr-mr;
    }
      
      
    }

    static void Read1()
    {
        string tmp = Console.ReadLine();
        N = int.Parse(tmp);
    }

    static void Read2()
    {
      
        string[] tmp=Console.ReadLine().Split(' ');
for(int i=0;i<N;i++){s.Add(int.Parse(tmp[i]));}

}
}