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: Runtime Error)

using System;
using System.Linq;
using System.Collections.Generic;

class MondaiC
{
    static void Main()
    {
        var line = Console.ReadLine().Split(' ').Select(x => Int32.Parse(x)).ToArray();
        var kenList = new List<long>();
        var shiList = new List<long>();
        for (int i=0;i<line[1];++i)
        {
            var shi=Console.ReadLine().Split(' ').Select(x => Int64.Parse(x)).ToArray();
            kenList.Add(shi[0]);
            shiList.Add(shi[1]);
        }
        var narabi=shiList.OrderBy(x=>x).ToArray();
        var ansArray = new string[line[1]];
        var kenArray = new int[line[1]];
        for (int i=0;i<line[1];++i)
        {
            var index = shiList.Select((c, d) => new { Content = c, Index = d }).First(x=>x.Content==narabi[i]).Index;
            ansArray[index] = string.Format("{0:D6}",kenList[index]);
            kenArray[kenList[index]]++;
            ansArray[index]+= string.Format("{0:D6}", kenArray[kenList[index]]);
        }
        foreach(var a in ansArray){
            Console.WriteLine(a);
        }
    }
}