Given an integer array nums that does not contain any zeros, find the largest positive integer k such that -k also exists in the array. Return the positive integer k. If there is no such integer, return -1. Example 1: Input: nums = [-1,2,-3,3] Output: 3 Explanation: 3 is the only valid k we can find in the array. Example 2: Input: nums = [-1,10,6,7,-7,1] Output: 7 Explanation: Both 1 and 7 have their corresponding negative values in the array. 7 has a larger value.