intial_input = input().split(" ")
n = int(intial_input[0])
if len(intial_input) > 1:
    s = str(intial_input[1])
else:
    s = ""
undo = []
for i in range(n):
    operation = input().split(" ")
    if operation[0] == '1':
        undo.append(s)
        s = s + (operation[1])
    elif operation[0] == '2':
        undo.append(s)
        x = len(s)
        s = s[0:x-int(operation[1])]
    elif operation[0] == '3':
        x = int(operation[1])-1
        print(s[x])
    elif operation[0] == '4':
        s = undo.pop()