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 Ruby (2.3.3) (judge verdict: Wrong Answer)

# C - Successive Subtraction	
n = gets.to_i
a = gets.split(" ").map{|k|k.to_i}
a = a.sort
sum = 0
if a[0]<0 && a[-1]<0 then
    d = a[-1]
    a.map{|s| sum += s.abs}
    sum = sum - 2*d
elsif a[0]>0 && a[-1]>0 then
    d = a[0]
    a.map{|s| sum += s.abs}
    sum = sum - 2*d
else
    a.map{|s| sum += s.abs}
end
puts sum
i = 0
while a[1+i] < 0
    puts "#{a[-1]} #{a[i]}"
    a[-1] = a[-1]-a[i]
    i += 1
end
ans_num = a[i]
(a.size-2-i).times{|k|
    puts "#{ans_num} #{a[n-1-1-k]}"
    ans_num = ans_num-a[n-1-1-k]
}
puts "#{a[-1]} #{ans_num}"