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 Kotlin (1.0.0) (judge verdict: Accepted)

import java.util.*
import java.math.*

fun main(args: Array<String>) {

//    var N = readLine()!!.split(" ").map { it.toInt() }
    var N = readLine()!!.toInt()
//    val D = readLine()!!.split(" ").map { it.toLong() }
    val A = readLine()!!.split(" ").map { it.toInt() }.toIntArray()

    val mod = 1000000007L

    A.sort()
    var sum = 0
    var ans = mutableListOf<String>()

    if (N == 2) {
        var max = Math.max(A[0], A[1])
        var min = Math.min(A[0], A[1])
        println(max-min)
        println("${max} $min")
        return
    }


    if(A[0] > 0 && A[N-1] > 0) {

        var tmp = A[0] -A[1]

        ans.add("${A[0]} ${A[1]}")

        for (i in  2 until N-1){
            ans.add("${tmp} ${A[i]}")
            tmp -= A[i]
        }
        ans.add("${A[N-1]} ${tmp}")
        sum = A[N-1] - tmp

    }else if(A[0] < 0 && A[N-1] < 0) {
        var tmp = A[N-1] -A[N-2]
        ans.add("${A[N-1]} ${A[N-2]}")

        for (i in  2 until N){
            ans.add("${tmp} ${A[N-1-i]} ")
            tmp -= A[N-1-i]
        }
        sum = tmp

    }
    else{
        var f = A.first()
        var l = A.last()

        for (i in 1 until N - 1) {
            var a = A[i]
            if (a > 0) {
                ans.add("${f} ${a}")
                f -= a
            } else {
                ans.add("${l} ${a}")
                l -= a
            }
        }
        ans.add("${l} ${f}")
        sum = l - f
    }
    println(sum)
    println(ans.joinToString("\n"))

//    println("%.9f".format(ans))
}