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 Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

/**
 * Created at 20:44 on 2019-06-15
 */

import java.io.*;
import java.util.*;
import java.math.BigInteger;

public class Main {

  static FastScanner sc = new FastScanner();

  static ArrayList<Long> A = new ArrayList();

  public static void main(String[] args) {

    int N = sc.nextInt();

    for (int i=0; i<N; i++) {
      A.add(sc.nextLong());
    }

    Collections.sort(A);

    /*
    long sum = 0;
    for (int i=0; i<N/2; i++) {
      sum -= A.get(i);
    }
    for (int i=(int)Math.floor(N/2.0); i<N; i++) {
      sum += A.get(i);
    }
    */

    //System.out.println(sum);

      boolean plus = true;
    ArrayList<String> outputs = new ArrayList();
    while(A.size() > 1) {
      ArrayList<Long> B = new ArrayList();
      plus = (A.size() % 2 == 1) ? A.get(A.size()/2) < 0 : true;
      while(A.size() > 1) {
        long a = A.remove(0);
        long b = A.remove(A.size()-1);
        if (plus) {
          outputs.add(b + " " + a);
          B.add((int)Math.ceil(B.size()/2.0), b - a);
        } else {
          outputs.add(a + " " + b);
          B.add((int)Math.floor(B.size()/2.0), a - b);
        }
        plus = !plus;
      }

      if (A.size() == 1) {
        int index = Collections.binarySearch(B, A.get(0));
        if (index >= 0) B.add(index, A.get(0));
        else B.add(-index-1, A.get(0));
      }
      
      Collections.sort(B);
      A = B;
    }

    System.out.println(A.get(0));
    for (String output : outputs) {
      System.out.println(output);
    }

  }



  static class Debugger {

    static long startTime;
    static boolean on = true;

    //入力受け取り後に呼び出す(入力時間をカウントしないため)
    static void start() {
      startTime = System.currentTimeMillis();
    }

    static void printTime() {
      if (on) System.out.println("(" + (System.currentTimeMillis() - startTime) + "ms)");
    }

    static void toggle() {
      on = !on;
    }

  }

  static class BigInt extends BigInteger {

    BigInteger MOD = new BigInteger("1000000007");
    static BigInt ZERO = new BigInt(0);
    static BigInt ONE = new BigInt(1);
    static BigInt TEN = new BigInt(10);

    public BigInt(long l) {
      super(Long.toString(l));
    }

    public BigInt(BigInteger i) {
      super(i.toByteArray());
    }

    public BigInt pow(int i) {
      return new BigInt(super.pow(i));
    }

    public BigInt[] divideAndRemainder(long l) {
      return divideAndRemainder(new BigInt(l));
    }

    public BigInt[] divideAndRemainder(BigInt i) {
      BigInt[] ret = new BigInt[2];
      BigInteger[] dAndR = super.divideAndRemainder(i);
      ret[0] = new BigInt(dAndR[0]);
      ret[1] = new BigInt(dAndR[1]);
      return ret;
    }

    public BigInt mod(long l) {
      return mod(new BigInt(l));
    }

    public BigInt mod(BigInt i) {
      return new BigInt(super.mod(i));
    }

    public BigInt mod() {
      return new BigInt(super.mod(MOD));
    }

    public BigInt add(long l) {
      return add(new BigInt(l));
    }

    public BigInt add(BigInt i) {
      return new BigInt(super.add(i));
    }

    public BigInt subtract(long l) {
      return subtract(new BigInt(l));
    }

    public BigInt subtract(BigInt i) {
      return new BigInt(super.subtract(i));
    }

    public BigInt multiply(long l) {
      return multiply(new BigInt(l));
    }

    public BigInt multiply(BigInt i) {
      return new BigInt(super.multiply(i));
    }

    public BigInt divide(long l) {
      return divide(new BigInt(l));
    }

    public BigInt divide(BigInt i) {
      return new BigInt(super.divide(i));
    }

    public BigInt abs() {
      return new BigInt(super.abs());
    }

  }

  /*
    add()でインデックスを指定しない場合指定されたソート順に違わない位置に追加する
    (ただしソートされていることが前提となる)
    Comparatorが0を返したとき、それらの順序は保証しない
    (TreeSet, TreeMapと違い削除はしない)
   */
  static class TreeList<E> extends ArrayList<E> {

    Comparator<? super E> comparator;

    TreeList(Comparator<? super E> c) {
      super();
      comparator = c;
    }

    /*
      ソート済みのリストに要素を追加する
     */
    public boolean add(E e) {
      int lowIndex = 0;
      int highIndex = size() - 1;
      int index = 0;

      if (size() == 0) {
        super.add(e);
        return true;
      }

      if (comparator.compare(e, get(0)) < 0) {
        index = 0;
      } else if (comparator.compare(e, get(highIndex)) > 0) {
        index = highIndex + 1;
      } else {
        while (lowIndex <= highIndex) {

          if (highIndex == lowIndex + 1 || highIndex == lowIndex) {
            index = highIndex;
            break;
          }

          int midIndex = (lowIndex + highIndex) / 2;
          ;

          if (comparator.compare(e, get(midIndex)) > 0) {
            lowIndex = midIndex;
          } else {
            highIndex = midIndex;
          }

        }
      }

      super.add(index, e);
      return true;
    }

  }

  static class FastScanner {
    private final InputStream in = System.in;
    private final byte[] buffer = new byte[1024];
    private int ptr = 0;
    private int buflen = 0;

    private boolean hasNextByte() {
      if (ptr < buflen) {
        return true;
      } else {
        ptr = 0;
        try {
          buflen = in.read(buffer);
        } catch (IOException e) {
          e.printStackTrace();
        }
        if (buflen <= 0) {
          return false;
        }
      }
      return true;
    }

    private int readByte() {
      if (hasNextByte()) return buffer[ptr++];
      else return -1;
    }

    private static boolean isPrintableChar(int c) {
      return 33 <= c && c <= 126;
    }

    private void skipUnprintable() {
      while (hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++;
    }

    public boolean hasNext() {
      skipUnprintable();
      return hasNextByte();
    }

    public String next() {
      if (!hasNext()) throw new NoSuchElementException();
      StringBuilder sb = new StringBuilder();
      int b = readByte();
      while (isPrintableChar(b)) {
        sb.appendCodePoint(b);
        b = readByte();
      }
      return sb.toString();
    }

    public long nextLong() {
      if (!hasNext()) throw new NoSuchElementException();
      long n = 0;
      boolean minus = false;
      int b = readByte();
      if (b == '-') {
        minus = true;
        b = readByte();
      }
      if (b < '0' || '9' < b) {
        throw new NumberFormatException();
      }
      while (true) {
        if ('0' <= b && b <= '9') {
          n *= 10;
          n += b - '0';
        } else if (b == -1 || !isPrintableChar(b)) {
          return minus ? -n : n;
        } else {
          throw new NumberFormatException();
        }
        b = readByte();
      }
    }

    public int nextInt() {
      return (int) nextLong();
    }
  }

}