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.*;

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