Integer Set Operations

You are required to implement an integer set with the following operations:

• add x: Add integer \( x \) to the set.
• delete x: Remove integer \( x \) from the set if it exists.
• exists x: Check whether integer \( x \) exists in the set. Output YES if it exists and NO otherwise.

You will be provided a sequence of queries. Each query is given in the form "command x". Process the queries in order and output the results of all exists queries.

The operations must be performed in an efficient manner. For example, for the exists query, the answer should be based on the current state of the set after performing all previous operations.

inputFormat

The first line contains an integer \( Q \) which denotes the number of queries. Each of the next \( Q \) lines contains a query in one of the following formats:

• add x
• delete x
• exists x

It is guaranteed that \( x \) is an integer.

outputFormat

For each query of type exists, output a line containing either YES or NO depending on whether \( x \) is present in the set.

## sample

8
add 1
add 2
exists 1
exists 3
add 3
exists 3
delete 3
exists 3

YES
NO
YES
NO

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