Problem:
Queue

Queue is a container of elements that are inserted and deleted according to FIFO (First In First Out).

For $n$ queues $Q_i$ ($i = 0, 1, ..., n-1$), perform a sequence of the following operations.

enqueue($t$, $x$): Insert an integer $x$ to $Q_t$.

front($t$): Report the value which should be deleted next from $Q_t$. If $Q_t$ is empty, do nothing.

dequeue($t$): Delete an element from $Q_t$. If $Q_t$ is empty, do nothing.

In the initial state, all queues 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 enqueue, front and dequeue operations respectively.

Output

For each front 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

1
4
2

Solution in C# (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;

namespace _0030
{
    class Program
    {
        static int[] head;
        static List<long>[] que;

        static void Inqueue(int num, long key)
        {
            if(head[num] == -1)
            {
                head[num] = 0;
            }
            que[num].Add(key);
        }

        static long Front(int num)
        {        
            return que[num][head[num]];
        }

        static void Dequeue(int num)
        {
            if(head[num] > que[num].Count - 1 || head[num] == -1)
            {
                return;
            }
            head[num]++;
        }


        static void Initial(int k)
        {
            for(int i = 0; i < k; i++)
            {
                head[i] = -1;
                que[i] = new List<long>();
            }
        }

        static void Main(string[] args)
        {

            string[] str = Console.ReadLine().Split(' ');

            int n = int.Parse(str[0]);
            int q = int.Parse(str[1]);

            que = new List<long>[q];

            head = new int[n];

            Initial(n);
            
            for(int i = 0; i < q; i++)
            {
                string[] input = Console.ReadLine().Split(' ');

                int order = int.Parse(input[0]);
                int num = int.Parse(input[1]);

                if(order == 0)
                {
                    long key = long.Parse(input[2]);
                    Inqueue(num, key);
                }
                else if(order == 1)
                {
                    if (head[num] > que[num].Count - 1 || head[num] == -1)
                    {
                        continue;
                    }
                    Console.WriteLine(Front(num));
                }
                else
                {
                    Dequeue(num);
                }
            }

        }
    }
}