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: Accepted)

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

namespace question3
{
    class Program
    {
        static void Main(string[] args)
        {
            var p = new Program();
            p.Run();
        }

        void Run()
        {
            var line1 = Console.ReadLine();
            var n = int.Parse(line1.Split(' ')[0]);
            var m = int.Parse(line1.Split(' ')[1]);

            var inputs = new List<Tuple<int,int>>();
            var cities = new List<Tuple<int, int, int>>[n];
            var citiesNumbers = new Dictionary<Tuple<int, int>, string>();

for(int i=0;i<n;i++){
    cities[i] = new List<Tuple<int,int,int>>();
}
            for (int i = 0; i < m; i++)
            {
                var line = Console.ReadLine().Split(' ');
                var pi = int.Parse(line[0]);
                var yi = int.Parse(line[1]);

                inputs.Add(new Tuple<int,int>(pi,yi));
                cities[pi-1].Add(new Tuple<int, int, int>(pi, yi, i));
            }

            for (int i = 0; i < n; i++)
            {
                var list = cities[i].OrderBy(e => e.Item2);
                var c = 0;
                foreach (var elem in list)
                {
                    citiesNumbers.Add(new Tuple<int, int>(elem.Item1, elem.Item2), String.Format("{0:000000}{1:000000}", elem.Item1, c + 1));
                    c++;
                }
            }

            foreach(var i in inputs){
                Console.WriteLine($"{citiesNumbers[Tuple.Create(i.Item1,i.Item2)]}");
            }
        }
    }
}