https://leetcode.com/problems/largest-positive-integer-that-exists-with-its-negative


Success


```python
class Solution:
    def findMaxK(self, nums: List[int]) -> int:
        new_nums = set()
        for num in nums:
            if num > 0:
                if -1*num in nums:
                    new_nums.add(num)
        if len(new_nums) == 0:
            return -1
        return max(new_nums)
```