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;
using static System.Console;
namespace AtCorder
{
    class Program
    {

        static void Main(string[] args)
        {
            int n, m;
            //List<City> cities = new List<City>();

            var ip1 = ReadLine().Split(' ');
            n = int.Parse(ip1[0]);
            m = int.Parse(ip1[1]);

            List<List<City>> sortedcs = new List<List<City>>();
            for (int i = 0; i < n; i++)
            {
                sortedcs.Add(new List<City>());
                sortedcs[i] = new List<City>();
            }

            for (int i = 0;i < m;i++)
            {
                var ip = ReadLine().Split(' ');
                int p, y;
                p = int.Parse(ip[0]);
                y = int.Parse(ip[1]);
                sortedcs[p-1].Add(new City(p,y));
            }

            for(int i = 0; i< n; i++)
            {
                sortedcs[i] = sortedcs[i].OrderBy(x=>x.y).ToList();
            }

            for(int i = 0;i < n; i++)
            {
                int rank = 1;
                foreach (var c in sortedcs[i])
                {
                    c.id = string.Format("{0:000000}{1:000000}", c.p, rank);
                    rank++;
                }
            }

            for(int i = 0;i < n; i++)
            {
                foreach(var c in sortedcs[i])
                WriteLine(c.id);
            }

        }

        class City
        {
            public int y;
            public int p;
            public string id;
            public City(int p,int y)
            {
                this.y = y;
                this.p = p;
            }
        }

        
    }
}