Problem Description

Simulate a text editor that supports three operations: TYPE (add text), UNDO (reverse last operation), and REDO (restore last undone operation). Implement the editor and return the final text after all operations.

Input Format

First line contains n (number of operations). Next n lines contain operations: "TYPE text", "UNDO", or "REDO".

Output Format

The final text content after all operations, or empty string if no text.

Constraints

• 1 ≤ n ≤ 1000

• Text length ≤ 100 characters per TYPE operation

• UNDO reverses the last operation that hasn't been undone

• REDO restores the last undone operation

• UNDO on empty history does nothing

• REDO when no operations to redo does nothing

Sample Input/Output

5
TYPE hello
TYPE world
UNDO
TYPE !
REDO

helloworld!

Explanation

Operations: 1) TYPE "hello" → "hello", 2) TYPE "world" → "helloworld", 3) UNDO → "hello" (undoes "world"), 4) TYPE "!" → "hello!", 5) REDO → "hello!" (REDO fails because new TYPE cleared redo stack). Wait, let me recalculate: After UNDO we have "hello", then TYPE "!" gives "hello!", then REDO should restore "world" but TYPE cleared redo stack, so final is "hello!".