Score : 500 points
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.
Find the maximum possible value of the final integer on the blackboard and a sequence of operations that maximizes the final integer.
Input is given from Standard Input in the following format:
N A_1 A_2 ... A_N
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}
3 1 -1 2
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.
3 1 1 1
1 1 1 1 0