class Stack:
    def __init__(self):
        self.name=''
        self.items=['']
        
    def push(self, char):
        self.items.append(self.name+char)
        return self.name+char
    
    def delete(self, k):
        self.name=self.name[:-k]
        self.items.append(self.name)
        
    def undo(self):
        self.items.pop()
        self.name=self.items[-1]
    
    def is_empty(self):
        return self.name == ''

Q=int(input().strip())
string = Stack()
for _ in range(Q):
    x= input().split()
    if x[0]=='1':
        string.name=string.push(x[1])
    elif x[0]=='2':
        string.delete(int(x[1]))
    elif x[0]=='3':
        print(string.name[int(x[1])-1])
    elif x[0]=='4':
        string.undo()