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: Runtime Error)

M = int(input())
A = list(map(int, input().split()))
A.sort()

saidainosuuji = A[-1]
saishounosuuji = A[0]
if len(A) <= 2:
    A = []
else:
    A = A[1:-1]

fuidx = 0
while A[fuidx] < 0:
    fuidx += 1

if 0 < fuidx <= len(A):
    fu = A[:fuidx]
else:
    fu = []
if fuidx < len(A):
    sei = A[fuidx:]
else:
    sei = []

sousa = []
# 最大値をつくる
for v in fu:
    sousa.append((saidainosuuji, v))
    saidainosuuji = saidainosuuji - v

# 最小値を作る
for v in sei:
    sousa.append((saishounosuuji, v))
    saishounosuuji = saishounosuuji - v

# 最後の値
sousa.append((saidainosuuji, saishounosuuji))
ans = saidainosuuji - saishounosuuji

print(ans)
for s in sousa:
    print(s[0], s[1])