import collections
import heapq
class Solution(object):
    def findNumsAppearOnce(self, nums):
        """
        :type nums: List[int]
        :rtype: List[int]
        """
        nums=collections.Counter(nums)
        # print(nums)
        res=heapq.nsmallest(2,nums,key=lambda x:nums[x])
        # print(res)
        return res