Unique Book Count

You are given a list of integer book IDs. Your task is to compute the number of unique book IDs in the list. In other words, you need to find the cardinality of the set of IDs.

Mathematically, if the list is represented as \(A = [a_1, a_2, \ldots, a_n]\), then the answer is \(|\{ a_i : 1 \leq i \leq n \}|\).

Input will be given from standard input and output should be sent to standard output.

inputFormat

The first line contains a single integer \(N\), representing the number of books.

The second line contains \(N\) space-separated integers, where each integer represents a book ID.

outputFormat

Output a single integer — the number of unique book IDs in the list.

## sample

8
4 5 2 2 8 4 7 5

5

</p>