PYTHON SOLUTION

APPEND = 1 DELETE = 2 PRINT = 3 UNDO = 4

class TextEditor: def init(self, initial_str: str = ""): self.current_str = list(initial_str) self.stack = []

def append(self, s: str):

        self.stack.append("".join(self.current_str))

        self.current_str.extend(s)

def delete(self, k: int):

        self.stack.append("".join(self.current_str))

        self.current_str = self.current_str[:-k]

def print(self, k: int):

        print(self.current_str[k-1])

def undo(self):

        if self.stack:
                self.current_str = list(self.stack.pop())

def command(self, s: str):

        parts = s.split(maxsplit=1)
        op = int(parts[0])

        if op == APPEND:
                self.append(parts[1])
        elif op == DELETE:
                self.delete(int(parts[1]))
        elif op == PRINT:

self.print(int(parts[1])) elif op == UNDO: self.undo()

if name == "main": Q = int(input()) editor = TextEditor() for _ in range(Q): command = input().strip() editor.command(command)