Second Largest Unique Number

You are given a list of integers. Your task is to find the second largest unique number in the list. A number is considered unique if it appears at least once; however, duplicates should be discarded when determining the order. In other words, after removing duplicates, if there are at least two distinct numbers, output the second largest one. Otherwise, output None.

More formally, if the set of unique numbers is \(\{a_1, a_2, \dots, a_k\}\) sorted in descending order such that \(a_1 > a_2 > \cdots > a_k\), then your answer is \(a_2\) if \(k \ge 2\); otherwise, output \(\text{None}\).

inputFormat

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

If n is 0, the list is empty.

outputFormat

Output a single line. If there exists a second largest unique number in the list, print that number; otherwise, print None.

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10 4 10 1 4 -1 -3 3

4