Text Editor with Undo Operation

You are required to implement a simple text editor that supports four operations: Type, Delete, Get, and Undo.

The editor maintains a text (which is initially empty) and a history of operations. The operations are defined as follows:

• Type x: Append character \( x \) to the text.
• Delete: Delete the last character from the text (if the text is not empty).
• Get k: Output the \( k \)-th character in the text (1-indexed). If \( k \) is out of range, output an empty string.
• Undo: Undo the last Type or Delete operation (if any).

You should process a sequence of operations, and for every Get operation, output the result on a new line. All inputs are given via stdin and outputs should be written to stdout.

Note: The undo operation only reverts Type or Delete operations and does nothing if there is no operation to undo.

inputFormat

The first line of the input contains an integer \( n \) denoting the number of operations.

The following \( n \) lines each contain one operation in one of the formats:

• Type x
• Delete
• Get k
• Undo

outputFormat

For each Get operation, output the corresponding character on a new line. If the request is out of bounds, output an empty line.

## sample

8
Type a
Type b
Type c
Get 3
Delete
Get 2
Undo
Get 3

c
b
c

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