Problem:
Score: 300 points

Problem Statement

In Republic of Atcoder, there are N prefectures, and a total of M cities that belong to those prefectures.

City i is established in year Y_i and belongs to Prefecture P_i.

You can assume that there are no multiple cities that are established in the same year.

It is decided to allocate a 12-digit ID number to each city.

If City i is the x-th established city among the cities that belong to Prefecture i, the first six digits of the ID number of City i is P_i, and the last six digits of the ID number is x.

Here, if P_i or x (or both) has less than six digits, zeros are added to the left until it has six digits.

Find the ID numbers for all the cities.

Note that there can be a prefecture with no cities.

Constraints

1 \leq N \leq 10^5

1 \leq M \leq 10^5

1 \leq P_i \leq N

1 \leq Y_i \leq 10^9

Y_i are all different.

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N M
P_1 Y_1
:
P_M Y_M

Output

Print the ID numbers for all the cities, in ascending order of indices (City 1, City 2, ...).

Sample Input 1

2 3
1 32
2 63
1 12

Sample Output 1

000001000002
000002000001
000001000001

As City 1 is the second established city among the cities that belong to Prefecture 1, its ID number is 000001000002.

As City 2 is the first established city among the cities that belong to Prefecture 2, its ID number is 000002000001.

As City 3 is the first established city among the cities that belong to Prefecture 1, its ID number is 000001000001.

Sample Input 2

2 3
2 55
2 77
2 99

Sample Output 2

000002000001
000002000002
000002000003

Solution in C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;

namespace ID
{

    class City
    {
        public int Order;
        public long Id;
        public City(int o, long i)
        {
            Order = o;
            Id = i;
        }
    }
    class Program
    {
        public static void Main(string[] args)
        {
            using (var sc = new SetConsole())
            {
                var nm = GetArrayIntInput();
                List<City>[] Prefectures = new List<City>[nm[0] + 1];
                for (int i = 1; i <= nm[0]; i++) { Prefectures[i] = new List<City>(); }
                for (int i = 1; i <= nm[1]; i++)
                {
                    var py = GetArrayIntInput();
                    Prefectures[py[0]].Add(new City(i, py[1]));
                }

                var results = new List<City>();
                for (int i = 1; i <= nm[0]; i++)
                {
                    Prefectures[i] = Prefectures[i].OrderBy(p => p.Id).ToList();
                    for (int j = 0; j < Prefectures[i].Count; j++)
                    {
                        Prefectures[i][j].Id = i * 1000000 + j + 1;
                        results.Add(Prefectures[i][j]);
                    }
                }

                foreach (var id in results.OrderBy(r => r.Order).Select(r => r.Id))
                {
                   CWrite(Convert.ToString(id, 10).PadLeft(12, '0'));
                }
            }
        }

        static string[] GetArrayCharInput() => Console.ReadLine().Split();
        static int[] GetArrayIntInput() => Console.ReadLine().StringToIntArray();
        static int GetIntInput() => Console.ReadLine().ToInt();
        static void CWrite(string str) => Console.WriteLine(str);
    }
    

    class SetConsole : IDisposable
    {
        public SetConsole()
        {
            var sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
            Console.SetOut(sw);
        }
        public void Dispose()
        {
            Console.Out.Flush();
        }
    }

    static class ExtentionsLibrary
    {
        public static int[] StringToIntArray(this string str) =>
            str.Split().Select(int.Parse).ToArray();
        public static int ToInt(this string str) => int.Parse(str);
    }
}