Count Unique Domains from Email Addresses

In many data processing tasks, it is often required to count the number of unique domains from a list of email addresses. Here, an email address is in the form (username@domain). Your task is to extract the domain part (i.e., the part after the '@' character) from each email in the given input and then output the number of unique domains.

For example, given the email addresses alice@example.com and bob@example.com, the domain example.com appears twice but should only be counted once. In mathematical terms, if (E = {e_1, e_2, \dots, e_n}) where each (e_i = \text{username}@\text{domain}), then you are to compute (|{ domain : e_i \in E }|), i.e. the cardinality of the set of domains.

inputFormat

The input is read from stdin and is formatted as follows:

(n) — an integer representing the number of email addresses.
Followed by (n) lines, each containing one email address.

Note: (n) can be zero; in that case, the output should be 0.

outputFormat

Print to stdout a single integer — the number of unique domain names extracted from the email addresses.## sample

5
alice@example.com
bob@example.com
charlie@example.org
dave@example.com
eve@example.org

2