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 C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include<bits/stdc++.h>
using namespace std;
int n;
vector<int> v;
vector<pair<int,int> > ans;
int main()
{
	cin>>n;
	for(int i=0;i<n;i++)
	{
		int a;
		cin>>a;
		v.push_back(a);
	}
	sort(v.begin(),v.end());
	int MIN=v[0],MAX=v[v.size()-1];
	for(int i=1;i<v.size()-1;i++)
	{
		if(v[i]<=0)
		{
			ans.push_back(make_pair(MAX,v[i]));
			MAX-=v[i];
		}
		else
		{
			ans.push_back(make_pair(MIN,v[i]));
			MIN-=v[i];
		}
	}
	ans.push_back(make_pair(MAX,MIN));
	MAX-=MIN;
	cout<<MAX<<endl;
	for(int i=0;i<ans.size();i++)
		cout<<ans[i].first<<" "<<ans[i].second<<endl;
	return 0;
}