Count Distinct Students

Given M check-ins and a list of checkpoint student IDs, determine the number of distinct student IDs. Essentially, you are to compute the cardinality of the set of IDs, i.e. $$|\{IDs\}|$$.

This problem tests your ability to use basic data structures such as sets to filter out duplicate entries.

inputFormat

The input is provided via stdin and consists of two lines:

1. The first line contains a single integer $$M$$ representing the total number of check-ins.
2. The second line contains $$M$$ space-separated integers (student IDs).

outputFormat

Output a single integer on stdout representing the count of distinct student IDs.

5
123 456 789 123 456

3