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

namespace AtCoder
{
    class Program
    {
        static void Main(string[] args)
        {
            var vals = Console.ReadLine().Split(' ').Select(x => int.Parse(x)).ToArray();
            var N = vals[0];
            var M = vals[1];

            var dict = new Dictionary<int, City>();
            foreach(var i in Enumerable.Range(0, M))
            {
                var item = new City(i + 1, Console.ReadLine());
                dict[item.Id] = item;
            }

            //Sort
            foreach(var i in Enumerable.Range(0, N))
            {
                var query = dict.Where(x => x.Value.Prefecture == i+1).OrderBy(x => x.Value.Year);
                var cnt = 0;
                foreach(var q in query)
                {
                    q.Value.SetPrefectureIndex(cnt);
                    cnt++;
                }
            }

            //View
            foreach(var d in dict)
            {
                Console.WriteLine(d.Value.GetID());
            }
        }
    }

    public class City
    {
        public int Id { get; set; }
        public int Prefecture { get; set; }
        public int Year { get; set; }

        public int PrefectureIndex { get; private set; }

        public City(int idx, string input)
        {
            Id = idx;
            var vals = input.Split(' ').Select(x => int.Parse(x)).ToArray();
            Prefecture = vals[0];
            Year = vals[1];
        }

        public void SetPrefectureIndex(int index)
        {
            PrefectureIndex = index;
        }

        public string GetID()
        {
            var str_id = $"{Prefecture:D6}{(PrefectureIndex+1):D6}";
            return str_id;
        }
    }

}