S, history = [], []
Q = int(input())    # no. of operations
for i in range(Q):
    op = input().split()
    
    if op[0] == "1":    # append()
        chars = op[1]
        S.extend(chars)
        history.append(("1", chars))
        
    elif op[0] == "2":  # delete()
        k = int(op[1])
        deleted = "".join(S[-k: ])
        history.append(("2", deleted))
        S = S[: -k]
        
    elif op[0] == "3":  # print()
        k = int(op[1]) - 1
        print(S[k])
        
    else:   # undo() either "1" or "2":
        last_op, chars = history.pop()
        if last_op == "1":
            S = S[: -len(chars)]
        elif last_op == "2":
            S.extend(chars)