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;

namespace ABC113C
{
    class Program
    {
        static void Main(string[] args)
        {
            var NM = Console.ReadLine().Split().Select(int.Parse).ToArray();
            var N = NM[0];
            var M = NM[1];
            
            City[] cities = new City[M];
            for (int i = 0; i < M; i++)
            {
                var PY = Console.ReadLine().Split().Select(int.Parse).ToArray();
                cities[i] = new City(PY[1], PY[0]);
            }

            cities = cities.OrderBy(x => x.Year).ThenBy(x=>x.Prefecture).ToArray();

            int nowPrefecture = -1;
            int nowCount = 1;
            for(int i = 0; i < M; i++)
            {
                if (cities[i].Prefecture != nowPrefecture)
                {
                    nowPrefecture = cities[i].Prefecture;
                    nowCount = 1;
                }
                cities[i].NumberInPrefecture = nowCount;
                nowCount++;
            }
            cities = cities.OrderBy(x => x.CityNumber).ToArray();
            for (int i = 0; i < M; i++)
            {
                Console.WriteLine(cities[i].CognitionNumber);
            }
            Console.ReadKey();
        }

        class City
        {
            static int CityNumberCount = 1;

            public int CityNumber;
            public int Year;
            public int Prefecture;
            public int NumberInPrefecture;
            
            public City(int year, int prefecture)
            {
                CityNumber = CityNumberCount;
                CityNumberCount++;
                Year = year;
                Prefecture = prefecture;
            }

            string P
            {
                get
                {
                    return FillZero(Prefecture);
                }
            }
            string x
            {
                get
                {
                    return FillZero(NumberInPrefecture);
                }
            }

            public string CognitionNumber
            {
                get
                {
                    return P + x;
                }
            }

            private string FillZero(int number)
            {
                return string.Format("{0:000000}", number);
            }
        }
    }
}