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: Runtime Error)

#include <iostream>
#include <vector>
#include<list>
#include <algorithm>
#include <string>
#include <math.h>
#include<map>
#include <utility>

#include<queue>
using namespace std;
#define REP(i,k,n) for(int i=k;i<n;i++)
 
#define INF 1844674407370955161
typedef long long int ll;
#define SIZE_OF_ARRAY(array) (sizeof(array)/sizeof(array[0]))
#define MOD 1000000007

template<typename T>
int vector_finder(std::vector<T> vec, T number) {
  auto itr = std::find(vec.begin(), vec.end(), number);
  size_t index = std::distance( vec.begin(), itr );
  if (index != vec.size()) { // 発見できたとき
    return 1;
  }
  else { // 発見できなかったとき
    return 0;
  }
}

template<typename T>
T gcd(T a,T b){
	if(b>0){
		return gcd(b, a % b);
	}else{
		return a;
	}
}

template<typename T>
T lcm(T a,T b){
	T g = gcd(a, b);
	return a * b / g;
}

void clear( std::queue<pair<int,int> > &q )
{
   std::queue<pair<int,int> > empty;
   std::swap( q, empty );
}
bool IsPrime(int num)
{
    if (num < 2) return false;
    else if (num == 2) return true;
    else if (num % 2 == 0) return false; // 偶数はあらかじめ除く

    double sqrtNum = sqrt(num);
    for (int i = 3; i <= sqrtNum; i += 2)
    {
        if (num % i == 0)
        {
            // 素数ではない
            return false;
        }
    }

    // 素数である
    return true;
}
template<typename T>
std::vector<T> enum_div(T n)//nの約数を列挙
{
	std::vector<T> ret;
	for(T i=1 ; i*i<=n ; ++i)
	{
		if(n%i == 0)
		{
			ret.push_back(i);
			if(i!=1 && i*i!=n)
			{
				ret.push_back(n/i);
			}
		}
	}
	return ret;
}


class DisjointSet{
    public:
        vector<int> rank, p;

        DisjointSet(){
        }

        DisjointSet(int size){
            rank.resize(size, 0);
            p.resize(size, 0);
            for (int i = 0; i < size;i++){
                makeSet(i);
            }
        }
        void makeSet(int x){
            p[x] = x;
            rank[x] = 0;
        }

        bool same(int x,int y){
            return findSet(x) == findSet(y);
        }
        void unite(int x,int y){
            link(findSet(x), findSet(y));
        }
        void link(int x,int y){
            if(rank[x]>rank[y]){
                p[y] = x;
            }else{
                p[x] = y;
                if(rank[x]==rank[y]){
                    rank[y]++;
                }
            }
        }
        int findSet(int x){
            if(x!=p[x]){
                p[x] = findSet(p[x]);
            }
            return p[x];
        }
};

int main()
{
  int N;
  cin>>N;
  ll A[N];
  REP(i,0,N){
    cin>>A[i];
  }
  
  sort(A,A+N);
  vector<long long> x,y;
  int idx=0;
  bool flag=false;
  REP(i,0,N){
    if(A[i]>0){
      idx=i;
      flag=true;
      break;
    }
  }
  queue<ll> q;
  ll ma=A[N-1];
  if(!flag){
    
    x.push_back(ma);
    REP(i,0,N-1){
    y.push_back(A[i]);
    ma-=A[i];
    }
    
  }else if(idx==N-1){

    x.push_back(ma);
    REP(i,0,N-1){
    y.push_back(A[i]);
    ma-=A[i];
    }
  }else if(idx==0){
    if(N==2){
      x.push_back(A[N-1]);
      y.push_back(A[0]);
      ma-=A[0];
    }else{
      ll mi=A[0];
      REP(i,1,N-1){
        y.push_back(A[i]);
        x.push_back(mi);
        mi-=A[i];
      }
      x.push_back(ma);
      y.push_back(mi);
      ma-=mi;
    }
  }else{
    if(N==2){
      x.push_back(A[N-1]);
      y.push_back(A[0]);
      ma-=A[0];
    }else{
      ll mi=A[0];
      REP(i,idx,N-1){
        y.push_back(A[i]);
        x.push_back(A[0]);
        A[0]-=A[i];
      }
      REP(i,0,idx){
        y.push_back(A[i]);
        x.push_back(ma);
        ma-=A[i];
      }
      
    }
  }
  cout<<ma<<endl;
  REP(i,0,N-1){
    cout<<x[i]<<" "<<y[i]<<endl;
  }
}