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 AizuOnlineJudge {
    class Program {
        static void Main() {
            var nq = Console.ReadLine().Split().Select(int.Parse).ToArray();
            var stack = Enumerable.Range(0, nq[0]).Select(_ => new Stack<string>()).ToArray();
            for (var i = 0; i < nq[1]; ++i) {
                var query = Console.ReadLine().Split();
                var index = int.Parse(query[1]);
                switch (query[0]) {
                    case "0":
                        stack[index].Push(query[2]);
                        break;

                    case "1":
                        if (stack[index].Any()) {
                            Console.WriteLine(stack[index].Peek());
                        }
                        break;

                    case "2":
                        if (stack[index].Any()) {
                            stack[index].Pop();
                        }
                        break;
                }
            }
        }
    }
}