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: Accepted)

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

class Program
{
    /// <summary>
    /// 市を表します.
    /// </summary>
    class City
    {
        public City(int parent, int year)
        {
            this.Parent = parent;
            this.Year = year;
        }

        public int Parent { get; set; }
        public int Year { get; set; }

        // 県内で何番目に生まれたかを表します.
        public int InParentIndex { get; set; }
    }

    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];

        City []cities = new City[M];
        City []sequencialCities = new City[M];

        // 市のパラメーターを入力してもらいます.
        for(int i = 0; i < M; ++i)
        {
            var cityParameter = Console.ReadLine().Split(' ').Select( x => int.Parse(x) ).ToArray();

            // 県、年.
            var city = new City(cityParameter[0], cityParameter[1]);
            
            cities[i] = city;

            // 入力された並び順を記憶しておきます.
            // この順番で結果を表示します.
            sequencialCities[i] = city;
        }

        // 誕生した年で昇順ソートします.
        cities = cities.OrderBy( x => x.Year ).ToArray();

        // 何番目に属するかを記憶します.
        var ParentIndex = new int[N];

        for(int i = 0; i < M; ++i)
        {
            var city = cities[i];

            ++ParentIndex[city.Parent - 1];

            city.InParentIndex = ParentIndex[city.Parent - 1];
        }

        // 結果表示を行います.
        for(int i = 0; i < M; ++i)
        {
            var city = sequencialCities[i];

            var index = city.InParentIndex;

            Console.WriteLine(
                city.Parent.ToString().PadLeft(6, '0')
                +
                index.ToString().PadLeft(6, '0')
            );
        }

#if DEBUG
        Console.ReadLine();
#endif
    }
}