class strEditor :
    def __init__(self):
        self.setting = []
        self.temp = []
    def createSetting(self):
        for s in [input() for _ in range(int(input()))]:
            main = s.split(" ")
            code = main[0]
            command = None
            if len(main) >1:
                command = main[1] 
            self.setting.append({"code":code,"command":command})
        return self.setting

    def operationMethod(self,code, command, finalS,idx):
        if int(code) == 1:
            self.temp.append(finalS)
            finalS+=(command)
        elif int(code) == 2:
            if 0 <= int(command) <= len(finalS):
                self.temp.append(finalS)
                finalS = finalS[:-int(command)] 
        elif int(code) == 3:
            if 1 <= int(command) <= len(finalS):
                print(finalS[int(command)-1])
        elif int(code) == 4:
            finalS = self.temp.pop()
        else:
            print("Invalid operation code.")
        return finalS
        
    def runCommand(self):
        finalS = ''
        for idx in range(len(self.setting)):
            payloads = self.setting[idx]
            code = payloads["code"]
            command = payloads["command"]
            finalS = self.operationMethod(code, command, finalS,idx)
        return finalS
        
editor = strEditor()
editor.createSetting()
editor.runCommand()