class Solution:
    def singleNumber(self, nums: List[int]) -> int:
        nums = sorted(nums)

        curr = nums[0]
        curr_count = 1

        print(nums)
        for i in range(1,len(nums)):
            if (curr_count == 3):
                curr_count = 1
                curr = nums[i]
            else:
                if (nums[i] != curr):
                    return curr
                else:
                    curr_count += 1
        if (curr_count != 0):
            return curr
        return -1