Problem:
Stack

Stack is a container of elements that are inserted and deleted according to LIFO (Last In First Out).

For $n$ stack $S_i$ ($i = 0, 1, ..., n-1$), perform a sequence of the following operations.

push($t$, $x$): Insert an integer $x$ to $S_t$.

top($t$): Report the value which should be deleted next from $S_t$. If $S_t$ is empty, do nothing.

pop($t$): Delete an element from $S_t$. If $S_t$ is empty, do nothing.

In the initial state, all stacks are empty.

Input

The input is given in the following format.

$n \; q$
$query_1$
$query_2$
:
$query_q$

Each query $query_i$ is given by

0 $t$ $x$

or

1 $t$

or

2 $t$

where the first digits 0, 1 and 2 represent push, top and pop operations respectively.

Output

For each top operation, print an integer in a line.

Constraints

$1 \leq n \leq 1,000$

$1 \leq q \leq 200,000$

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

Sample Input 1

3 9
0 0 1
0 0 2
0 0 3
0 2 4
0 2 5
1 0
1 2
2 0
1 0

Sample Output 1

3
5
2

Solution in JAVA (judge verdict: Accepted)

import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Deque;
import java.util.List;
import java.util.Scanner;
import java.util.Set;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		List<Deque<Integer>> list = new ArrayList<>();
		int n = sc.nextInt();
		int q = sc.nextInt();
		for (int i = 0; i < n; i++) {
			list.add(new ArrayDeque<>());
		}
		for (int i = 0; i < q; i++) {
			switch (sc.nextInt()) {
				case 0:
					list.get(sc.nextInt()).addFirst(sc.nextInt());
					break;
				case 1:
					int t = sc.nextInt();
					if (!list.get(t).isEmpty()) {
						System.out.println(list.get(t).peekFirst());
					}
					break;
				case 2:
					t = sc.nextInt();
					if (!list.get(t).isEmpty()) {
						list.get(t).removeFirst();
					}
					break;
			}
		}
	}
}