Find Pair With Zero Sum

Given a list of integers, your task is to find a pair of numbers that sum to zero. If such a pair exists, output the pair as two integers separated by a space, where the first number is the additive inverse of the second. If there are multiple valid pairs, any one is acceptable. If no such pair exists, output None.

For example, given the list [2, -3, 1, -1, 3], one valid answer is 1 -1 because 1 + (-1) = 0.

inputFormat

The input is read from standard input. The first line contains an integer n which indicates the number of elements in the list. The second line contains n space-separated integers.

outputFormat

The output is written to standard output. If a pair is found, print the two integers separated by a space (i.e. if the pair is (a, b), print a b). If no such pair exists, print None.

5
2 -3 1 -1 3

1 -1