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++14 (judge verdict: Accepted)

#include <iostream>
#include <stack>
#include <vector>
using namespace std;

int main() {
	int n;
	cin >> n;
	vector<stack<int>> S(n);
	int q;
	cin >> q;
	for (int i = 0; i < q; ++i) {
		int query;
		cin >> query;
		if (query == 0) {
			int t, x;
			cin >> t >> x;
			S[t].push(x);
		}
		else if (query == 1) {
			int t;
			cin >> t;
			if (!S[t].empty()) cout << S[t].top() << endl;
		}
		else {
			int t;
			cin >> t;
			if (!S[t].empty()) S[t].pop();
		}
	}
}