Problem:
Vector

For a dynamic array $A = \{a_0, a_1, ...\}$ of integers, perform a sequence of the following operations:

pushBack($x$): add element $x$ at the end of $A$

randomAccess($p$):print element $a_p$

popBack(): delete the last element of $A$

$A$ is a 0-origin array and it is empty in the initial state.

Input

The input is given in the following format.

$q$
$query_1$
$query_2$
:
$query_q$

Each query $query_i$ is given by

0 $x$

or

1 $p$

or

2

where the first digits 0, 1 and 2 represent pushBack, randomAccess and popBack operations respectively.

randomAccess and popBack operations will not be given for an empty array.

Output

For each randomAccess, print $a_p$ in a line.

Constraints

$1 \leq q \leq 200,000$

$0 \leq p < $ the size of $A$

$-1,000,000,000 \leq x \leq 1,000,000,000$

Sample Input 1

8
0 1
0 2
0 3
2
0 4
1 0
1 1
1 2

Sample Output 1

1
2
4

Solution in Scala (judge verdict: Accepted)

import scala.collection.mutable.ArrayBuffer
import scala.io.StdIn.{readInt, readLine}

object Main extends App {
  val pushBack     = 0
  val randomAccess = 1
  val popBack      = 2

  val n     = readInt()
  val lines = Iterator.fill(n)(readLine())

  val orders = lines.map { _.split(" ").map { _.toInt } }
  var xs     = Vector[Int]()
  orders.foreach {
    case Array(`pushBack`, x)     => xs = xs :+ x
    case Array(`randomAccess`, x) => println(xs(x))
    case Array(`popBack`)         => xs = xs.init
  }
}