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 C# (judge verdict: Accepted)

using System;
using System.Linq;
using System.Collections.Generic;

class Test
{
    static void Main()
    {
        string[] r = Console.ReadLine().Split();
        int n = int.Parse(r[0]);
        int q = int.Parse(r[1]);

        Stack<int>[] A = new Stack<int>[n];
        for (int i = 0; i < n; i++)
        {
            A[i] = new Stack<int>();;
        }

        for (int i = 0; i < q; i++)
        {
            int[] array = Console.ReadLine().Split().Select(int.Parse).ToArray();

            switch (array[0])
            {
                case 0:
                    A[array[1]].Push(array[2]);
                    break;
                case 1:
                    if (A[array[1]].Count != 0) Console.WriteLine(A[array[1]].Peek());
                    break;
                case 2:
                    if (A[array[1]].Count != 0) A[array[1]].Pop();
                    break;
            }
        }
    }
}