Description

Managing books is a highly complex task, with many new books being added to a library every day. To facilitate easier book management (and to help patrons quickly determine if the books they need are available), we need to design a book search system.

This system needs to support two operations:

1. add(s) indicates adding a new book with the title s.
2. find(s) queries whether a book with the title s exists.

Input Format

The first line contains a positive integer $n$, representing the number of operations. The following $n$ lines each specify one of the two operations in the format:

add s
find s

There is a space separating the book title s and the command (add or find). We guarantee that the length of all book titles does not exceed $200$. The input data can be assumed to be accurate.

Output Format

For each find(s) command, you must output a corresponding line with yes or no, indicating whether the queried book currently exists in the library.

Note: Initially, the library contains no books. Additionally, book titles with the same letters but different cases are considered distinct.

Sample 1

4
add Inside C#
find Effective Java
add Effective Java
find Effective Java

no
yes

Constraints and Hints

$n \le {30000}$.