TV Show Recordings Manager

You are given a list of commands to manage a record of TV show recordings. The commands can be of three types:

• ADD show_name: Adds the TV show show_name to the recording list.
• REMOVE show_name: Removes the TV show show_name from the recording list if it exists.
• CHECK show_name: Checks whether the TV show show_name is currently scheduled for recording. For each CHECK command, output YES if it exists in the recording list, otherwise output NO.

The input is provided via standard input and for each CHECK command you should output the result on a new line in standard output.

The problem can be mathematically characterized using set operations. For example, if \( S \) denotes the set of recordings, then the commands transform \( S \) as follows:

• \( S = S \cup \{show\_name\} \) for an ADD command
• \( S = S \setminus \{show\_name\} \) for a REMOVE command
• Output \( YES \) if \( show\_name \in S \), otherwise output \( NO \) for a CHECK command

inputFormat

The first line contains an integer n denoting the number of commands. Each of the following n lines contains a command in one of the following forms:

• ADD show_name
• REMOVE show_name
• CHECK show_name

All commands are processed in the order they appear.

outputFormat

For each CHECK command encountered, output a single line containing either YES if the show is in the recording list or NO otherwise.

## sample

7
ADD GameOfThrones
ADD BreakingBad
CHECK GameOfThrones
REMOVE GameOfThrones
CHECK GameOfThrones
ADD TheCrown
CHECK TheCrown

YES
NO
YES

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