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;

namespace CSharp_AtCoder
{

    class Program
    {


        static void Main(string[] args)
        {
            int[] NM = Console.ReadLine().Split(' ').Select(x => int.Parse(x)).ToArray();
            int N = NM[0];
            int M = NM[1];

            Dictionary<int, int>[] prefs = new Dictionary<int, int>[N];
            int[] city_to_pref = new int[M];
            string[] id = new string[M];
            for (int i = 0; i < N; i++) prefs[i] = new Dictionary<int, int>();
            for(int city_num = 0; city_num < M; city_num++)
            {
                int[] PY = Console.ReadLine().Split(' ').Select(x => int.Parse(x)).ToArray();
                int pref_num = PY[0] - 1;
                int year = PY[1];

                city_to_pref[city_num] = pref_num; 
                prefs[pref_num][city_num] = year;

            }

            for (int pref_num = 0; pref_num < N; pref_num++)
            {
                // yearで昇順                
                int cnt = 1;
                foreach(var city_to_year in prefs[pref_num].OrderBy(x => x.Value))
                {
                    int city_num = city_to_year.Key;
                    int city_year = city_to_year.Value;

                    //city_numのidを求める
                    //pref_num(6) + cnt(6)
                    string left = (pref_num + 1).ToString();
                    for (int i = 0; i < 6 - left.Length; i++) left = "0" + left;
                    string right = cnt.ToString();
                    for (int i = 0; i < 6 - right.Length; i++) right = "0" + right;

                    id[city_num] = left + right;

                    cnt++;
                }
            }


            Console.WriteLine(string.Join("\n", id));

        }
    }
}