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: Time Limit Exceeded)

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

class Program
{
    /// <summary>
    /// 市を表します.
    /// </summary>
    class City
    {
        public City(int birthYear, int inPrefectureIndex)
        {
            this.BirthYear = birthYear;
            this.InPrefectureIndex = inPrefectureIndex;
        }

        /// <summary>
        /// 誕生した年を表します.
        /// </summary>
        public int BirthYear { get; set; }

        /// <summary>
        /// 属する県を表します.
        /// </summary>
        public int InPrefectureIndex { get; set; }
    }

    /// <summary>
    /// 県を表します.
    /// </summary>
    class Prefecture
    {
        /// <summary>
        /// 属する市を表します.
        /// </summary>
        List<City> cities = new List<City>();
        public List<City> Cities { get { return cities; } }
    }

    static void Main(string[] args)
    {
        // N個の県と M個の属する市を受け取ります.
        var parameter = Console.ReadLine().Split(' ').Select( x => int.Parse(x) ).ToArray();
        var N = parameter[0];
        var M = parameter[1];

        // 県を作成します.
        Prefecture[] prefectures = new Prefecture[N];
        for ( int n = 0; n < N; ++n )
        {
            prefectures[n] = new Prefecture();
        }
        
        // 表示するときに使用するので入力された市の順番を覚えます.
        var citySequence = new City[M];

        // M回入力を受け付けてパラメーターを取得します.
        for(int mi = 0; mi < M; ++mi)
        {
            // 属する県Pi と誕生した年Yi を受け取ります.
            var cityParameter = Console.ReadLine().Split(' ').Select( x => int.Parse(x) ).ToArray();
            
            City city = new City(birthYear: cityParameter[1], inPrefectureIndex: cityParameter[0] - 1); // Index.
            prefectures[city.InPrefectureIndex].Cities.Add(city);
            
            // 表示用に並べた市の一覧を表します.
            citySequence[mi] = city;
        }

        // 生まれた年で昇順ソートします.
        for(int n = 0; n < N; ++n)
        {
            if ( prefectures[n]?.Cities.Count < 2 ) continue;
            prefectures[n].Cities.Sort( (a, b) => a.BirthYear - b.BirthYear );
        }

        // 結果表示を行います.
        foreach(var element in citySequence)
        {
            // +1 することで表示するときの文字に直します.
            string left  = (element.InPrefectureIndex + 1).ToString().PadLeft(6, '0');
            string right = (prefectures[element.InPrefectureIndex].Cities.FindIndex( x => x == element ) + 1).ToString().PadLeft(6, '0');

            Console.WriteLine(left + right);
        }
    }
}