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.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		ArrayList<List<Integer>> A = new ArrayList<>();
		for (int i = 0; i < n; i++) {
			ArrayList<Integer> B = new ArrayList<>();
			A.add(B);
		}
		int q = sc.nextInt();
		for (int i = 0; i < q; i++) {
			int x = sc.nextInt();
			if (x == 0) {
				int y = sc.nextInt();
				int z = sc.nextInt();
				A.get(y).add(z);
			} else if (x == 1) {
				int y = sc.nextInt();
				if (A.get(y).size() != 0) {
					System.out.println(A.get(y).get(A.get(y).size() - 1));
				}
			} else if (x == 2) {
				int y = sc.nextInt();
				if (A.get(y).size() != 0) {
					A.get(y).remove(A.get(y).size() - 1);
				}
			}
		}
		sc.close();

	}

}