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 Python (3.4.3) (judge verdict: Wrong Answer)

N = int(input())
lst = list(map(int,input().split()))
so = sorted(lst)
if N % 2 == 0:	
	M = sum(so[len(so)//2:])-sum(so[:len(so)//2])
	print(M)
	for i in range(len(so)-1):
		if i == 0:
			print(so[-1],so[0])
			so.append(so[-1]-so[0])
			del(so[-2])
			del(so[0])
		elif i % 2 == 1:
			print(so[0],so[-1])
			so.append(so[0]-so[-1])
			del(so[-2])
			del(so[0])
		else:
			print(so[-2],so[-1])
			so.append(so[-2]-so[-1])
			del(so[-3])
			del(so[-2])
else:
	M = sum(so[(len(so)-1)//2:]) - sum(so[:(len(so)-1)//2])
	print(M)
	for i in range(len(so)-1):
		if i % 2 == 0:
			print(so[0],so[-1])
			so.append(so[0]-so[-1])
			del(so[-2])
			del(so[0])
		else:
			print(so[-2],so[-1])
			so.append(so[-2]-so[-1])
			del(so[-3])
			del(so[-2])