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)

#include<stdio.h>
#include<stdlib.h>
#define N 1000

typedef struct stack{
	int *a;
	int top;
}stack;

int main(){
	int n,q,i,x,y;
	int com;
	stack S[N];
	
	scanf("%d %d",&n,&q);
	
	for(i=0;i<n;i++){
		S[i].top=0;
		S[i].a=malloc(sizeof(int)*q);
	}
	
	for(i=0;i<q;i++){
		scanf("%d",&com);
		
		if(com==0){
			scanf("%d %d",&x,&y);
			S[x].a[(S[x].top)++]=y;
		}
		
		else if(com==1){
			scanf("%d",&x);
			if(S[x].top!=0)printf("%d\n",S[x].a[S[x].top-1]);
		}
		
		else if(com==2){
			scanf("%d",&x);
			if(S[x].top!=0)S[x].top--;
		}
	}
	
	return 0;
	
}