K and -K

Given a list of integers nums, return the largest integer k where k and -k both exist in nums (they can be the same integer). If there’s no such integer, return -1.

Constraints

• n ≤ 100,000 where n is the length of nums

https://binarysearch.com/problems/K-and-K

Examples

Example 1

Input

• nums = [-4, 1, 8, -5, 4, -8]

Output

• answer = 8

Example 2

Input

• nums = [5, 6, 1, -2]

Output

• answer = -1

Example 3

Input

• nums = [1, 2, 0, 3, 4]

Output

• answer = 0

Solution