Count Distinct Books

You are given an integer n which represents the number of books in a catalog, and a list of n integers representing the indices of the books. Your task is to count the number of distinct books in the catalog.

The problem can be mathematically expressed as finding \( |\{ indices \}| \), where \( \{ indices \} \) denotes the set of unique book indices.

Note: The input is provided via standard input and the output must be printed to standard output.

inputFormat

The first line contains an integer n representing the number of books. The second line contains n space-separated integers, each representing a book index.

outputFormat

Output a single integer denoting the number of distinct book indices.

5
1 2 3 4 5

5