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.Linq;
using System.Text;
using System.Threading.Tasks;

class Program
{
    static int N;
    static int M;

    class Comare : IComparer<int>
    {
        public int Compare(int x, int y)
        {
            return x - y;
        }
    }

    class CityInfo
    {
        public CityInfo(int k, int y, int c)
        {
            Ken = k;
            Year = y;
            CityNo = c;
        }

        public int Ken;
        public int Year;
        public int CityNo;
    }

    public static void Main(string[] args)
    {
        N = Input.NextInt();
        M = Input.NextInt();

        var Cities = new List<CityInfo>();
        var Kens = new Dictionary<int, List<CityInfo>>();
        for (int i = 0; i < M; i++)
        {
            var l = Input.LineInt();
            var ken_no = l[0];
            var city_born = l[1];

            if (!Kens.ContainsKey(ken_no))
                Kens[ken_no] = new List<CityInfo>();
            var city = new CityInfo(ken_no, city_born, 0);
            Cities.Add(city);
            Kens[ken_no].Add(city);
        }
        foreach (var en in Kens)
        {
            en.Value.Sort((a, b) => (a.Year - b.Year));
            for (int i = 0; i < en.Value.Count; i++)
            {
                en.Value[i].CityNo = i + 1;
            }
        }

        foreach (var city in Cities)
        {
            Console.WriteLine($"{Make6(city.Ken)} {Make6(city.CityNo)}");
        }
    }

    static string Make6(int x)
    {
        string s;
        s = "000000" + x.ToString();
        return s.Substring(s.Length - 6);
    }
}

public static class Input
{
    private static Queue<string> q = new Queue<string>();
    private static void Confirm() { if (q.Count == 0) foreach (var s in Console.ReadLine().Split(' ')) q.Enqueue(s); }
    public static int NextInt() { Confirm(); return int.Parse(q.Dequeue()); }
    public static long NextLong() { Confirm(); return long.Parse(q.Dequeue()); }
    public static string NextString() { Confirm(); return q.Dequeue(); }
    public static double NextDouble() { Confirm(); return double.Parse(q.Dequeue()); }
    public static int[] LineInt() { return Console.ReadLine().Split(' ').Select(int.Parse).ToArray(); }
    public static long[] LineLong() { return Console.ReadLine().Split(' ').Select(long.Parse).ToArray(); }
    public static string[] LineString() { return Console.ReadLine().Split(' ').ToArray(); }
    public static double[] LineDouble() { return Console.ReadLine().Split(' ').Select(double.Parse).ToArray(); }
}