First Unique Integer

You are given a list of integers. Your task is to find the first unique integer in the list, meaning the first number that appears exactly once when traversing the list from left to right. If no unique integer is found, output None.

Input: Standard input is used. The first line contains an integer n representing the number of elements, and the second line contains n space-separated integers.

Output: The first unique integer, or None if there is none.

inputFormat

The first line of input contains an integer n denoting the number of elements. The second line contains n integers separated by spaces.

outputFormat

Print the first unique integer. If no unique integer exists, print None.## sample

7
2 3 3 2 6 7 7

6