Second Highest Unique Number

Given a list of integers, your task is to find the second highest unique number in the list. A unique number is defined as one that appears only once in the list. If the list does not have at least two unique numbers, output None.

Note: The uniqueness is determined from the whole list regardless of order. For example, in the list [4, 3, 1, 4, 6], the unique numbers are 1, 3, 4, and 6, so the second highest unique number is 4.

inputFormat

The first line contains an integer n representing the number of integers. The second line contains n space-separated integers.

outputFormat

Output a single line containing the second highest unique number. If there is no such number, output None.

5
4 3 1 4 6

4