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.Generic;

class Program
{
    static void Main(string[] args)
    {
        var inputs = Console.ReadLine().Split(' ');
        var N = int.Parse(inputs[0]);
        var M = int.Parse(inputs[1]);
        var cityList = new List<City>(M);
        for (int i = 0; i < M; i++)
        {
            inputs = Console.ReadLine().Split(' ');
            var p = int.Parse(inputs[0]);
            var y = long.Parse(inputs[1]);
            var city = new City(i + 1, p, y);
            cityList.Add(city);
        }
        // 誕生年順にソートしておく
        cityList = cityList.OrderBy(ct => ct.Y).ToList();

        var dict = new Dictionary<long, List<City>>();
        for (int i = 0; i < M; i++)
        {
            var city = cityList[i];
            if (dict.ContainsKey(city.P))
            {
                dict[city.P].Add(city);
            }
            else
            {
                var list = new List<City>();
                list.Add(city);
                dict.Add(city.P, list);
            }
        }

        var codes = new string[M];
        for (int i = 1; i <= N; i++)
        {
            if (!dict.ContainsKey(i))
            {
                continue;
            }

            var list = dict[i];
            for (int j = 0; j < list.Count; j++)
            {
                var x = j + 1;
                var p = list[j].P;
                var value = p.ToString().PadLeft(6, '0') + x.ToString().PadLeft(6, '0');
                codes[list[j].id - 1] = value;
            }
        }

        foreach (var cd in codes)
        {
            Console.WriteLine(cd);
        }

    }

    struct Code
    {
        internal string value;
        internal int id;
        internal Code(int id, string value)
        {
            this.value = value;
            this.id = id;
        }
    }

    struct City
    {
        internal int id;
        internal int P;
        internal long Y;
        internal City(int id, int p, long y)
        {
            this.id = id;
            this.P = p;
            this.Y = y;
        }
    }

}