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>

int main(void)
{
    char line[20];
    fgets(line, 20, stdin);
    int n = atoi(line);

    int **S;
    int *S_i;
    S = malloc(sizeof(int *) * n);
    S_i = malloc(sizeof(int) * n * 200000);
    int i;
    for (i = 0; i < n; i++) {
        S[i] = S_i + i * 200000;
    }
    int *idx;
    idx = calloc(n, sizeof(int));

    char *a;
    a = line;
    while (*a >= '0') a++;
    int q;
    q = atoi(a + 1);

    int op, t, x;

    while (q--) {
        fgets(line, 20, stdin);
        op = atoi(line);
        a = line + 2;
        t = atoi(a);
        i = idx[t];
        if (op == 0) {
            while (*a >= '0') a++;
            x = atoi(a + 1);
            S[t][i] = x;
            idx[t] += 1;
        }
        else if (i != 0) {
            if (op == 1) printf("%d\n", S[t][i-1]);
            else idx[t] -= 1;
        }
    }

    free(S);
    free(S_i);
    free(idx);

    return 0;
}