A web server logs n visitor ID tokens over one day (the same visitor may be logged multiple times). Count how many distinct visitor IDs appear in the log.
Input format
Line 1: an integer n.
Line 2: n space-separated visitor ID tokens (case-sensitive alphanumeric strings, no spaces inside a token).
Output format
A single integer: the number of distinct visitor IDs.
Constraints
- 1 ≤ n ≤ 100000
- Each token has length 1-20 and consists of letters and digits only (case-sensitive).