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;
 
static class MainClass {
 
  public struct City{
    public long num;
    public long year;
    public int ID;
    public City(long n, long y, int i){
      num = n;
      year = y;
      ID = i;
    }

  }

  public static void Main (string[] args) {
    var temp = Console.ReadLine().Split(' ').Select(long.Parse);
    var N = temp.ElementAt(0);
    var M = temp.ElementAt(1);
    var CityList = new List<City>();

    for(var i = 0; i < M; i++){
     var temp2 = Console.ReadLine().Split(' ').Select(long.Parse);
      CityList.Add(new City(temp2.ElementAt(0), temp2.ElementAt(1),i));
    }
    
    var ans = new List<string>();

    var sorted = CityList.OrderBy(x => x.year).ThenBy(x => x.num);
    var count = 0;
    var prev = sorted.First().num;
    
    foreach(var c in sorted){
      count = prev == c.num ? count + 1 : 1;
      ans.Add(String.Format("{0:000000}", c.num) + String.Format("{0:000000}", count) + String.Format("{0:000000}", c.ID));
    }
    ans = ans.OrderBy(x => int.Parse(x.Substring(12))).Select(s => s.Substring(0,12)).ToList();

    ans.ForEach(Console.WriteLine);
  }
  
}