class Solution:
    def sumOfUnique(self, nums: List[int]) -> int:
        set_nums = set()
        set_second = set()

        for i in nums:
            if i in set_nums:
                set_nums.remove(i)
                set_second.add(i)
            else:
                if i not in set_second:
                    set_nums.add(i)
                
        return sum(set_nums)