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: Accepted)

n = int(input())
x = list(map(int,input().split()))
#x = sorted(list(map(int,input().split())),reverse=True)
#nmax = max(x)
#ans = 2*nmax-sum(x)
lst = []

  
nmi = min(x)
nma = max(x)
del x[x.index(nmi)]
del x[x.index(nma)]

mainus = [i for i in x if i < 0]
plus = [i for i in x if i >= 0]
for i in mainus:
  lst.append(str(nma)+" "+str(i))
  nma -= i
for i in plus:
  lst.append(str(nmi)+" "+str(i))
  nmi -= i
lst.append(str(nma)+" "+str(nmi))
print(nma-nmi)
for i in lst:
  print(i)
"""
while max(x) > -1 and len(x) > 1:
  mi = min(x)
  ma = max(x)
  lst.append(str(mi)+" "+str(ma))
  del x[x.index(mi)]
  del x[x.index(ma)]
  x.append(mi - ma)

for i in range(len(x)):
  lst.append(str(nma)+" "+str(i))
  nma += i
print(nmi - nma)
for i in range(len(lst)):
  print(lst[i])
print(nmi,nma)
"""