q = int(input())

s = ''
revert = [s]

for _ in range(q):
    line = input().strip().split()
    operation = int(line[0])
    try:
        argument = line[1]
    except Exception:
        pass
        
    match operation:
        case 1:
            revert.append(s)
            s += argument
        case 2:
            revert.append(s)
            for _ in range(int(argument)):
                s = s[:-1]
        case 3:
            print(s[int(argument)-1])
        case 4:
            s = revert.pop()