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;

namespace ConsoleApp
{
    class Program
    {
        static void Main(string[] args)
        {
            var str = Console.ReadLine();
            var strs = str.Split(' ');
            var N = int.Parse(strs[0]);
            var M = int.Parse(strs[1]);

            var PY = new List<List<int>>();
            for (int i = 0; i < M; i++)
            {
                str = Console.ReadLine();
                strs = str.Split(' ');

                var list = new List<int>();
                list.Add(i);
                list.Add(int.Parse(strs[0]));
                list.Add(int.Parse(strs[1]));
                list.Add(0);

                PY.Add(list);
            }

            PY = PY.OrderBy(py => py[1]).ThenBy(py => py[2]).ToList();

            var prevP = PY[0][1];
            var no = 1;
            for (int i = 0; i < PY.Count; i++)
            {
                if (prevP != PY[i][1])
                {
                    no = 1;
                }

                PY[i][3] = no++;
            }

            PY = PY.OrderBy(py => py[0]).ToList();

            foreach (var item in PY)
            {
                Console.WriteLine(item[1].ToString().PadLeft(6, '0') + item[3].ToString().PadLeft(6, '0'));
            }
        }
    }
}