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)

n=int(input())
xs=list(map(int,input().split()))
if len(xs) == 2:
    xs = sorted(xs)
    print(xs[1]-xs[0])
    print(xs[1],xs[0])
else:
    plus=sorted(x for x in xs if x >= 0)
    minus=sorted(x for x in xs if x < 0)
    proc = []
    if len(minus) > 1:
        nm = len(minus)
        minus = list(reversed(minus))
        for i in range(nm-2):
            if i == 0:
                proc.append((minus[0],minus[1]))
                b = minus[0] - minus[1]
            else:
                proc.append((b,minus[i+1]))
                b = b - minus[i+1]
        if nm == 2:
            b = minus[0]
        proc.append((minus[-1],b))
        b = minus[-1]-b
    elif minus:
        b = minus[0]
    else:
        b = None
    if b is not None:
        plus = [b] + plus
    np = len(plus)
    for i in range(np-2):
        if i == 0:
            proc.append((plus[0],plus[1]))
            a = plus[0] - plus[1]
        else:
            proc.append((a,plus[i+1]))
            a = a - plus[i+1]
    if np == 2:
        a = plus[0]
    proc.append((plus[-1],a))
    a = plus[-1]-a
    print(a)
    for x,y in proc:
        print(x,y)