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.Collections.Generic;
using System.Linq;

namespace CSharpSample01
{

    class Program
    {

        static int[,] stack;
        static int[] last;

        static void Push(int t, int key)
        {
            stack[t, last[t]] = key;            
            last[t]++;
        }


        static void Peek(int t)
        {      
            if(last[t] - 1 < 0)
            {
                return;
            }
            Console.WriteLine(stack[t, last[t] - 1]);
        }

        static void Pop(int t)
        {
            if(last[t] - 1 < 0)
            {
                return;
            }
            last[t]--;
        }


        static void Main(string[] args)
        {
            string[] input = Console.ReadLine().Split(' ');
            int n = int.Parse(input[0]);
            int q = int.Parse(input[1]);

            stack = new int[n, q];
            last = new int[n];

            int order;
            int t;
            int x;
            for(int i = 0; i < q; i++)
            {
                input = Console.ReadLine().Split(' ');

                order = int.Parse(input[0]);
                t = int.Parse(input[1]);

                if (order == 0)
                {
                    x = int.Parse(input[2]);
                    Push(t, x);
                }
                else if(order == 1)
                {

                    Peek(t);

                }
                else
                {
                    Pop(t);
                }

            }
                  
        }
    }
}