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.Collections.Generic; 
class Program
    {
       
        static void Main(string[] args)
        {
            string[] temp_d = Console.ReadLine().Split(' ');
            int N = int.Parse(temp_d[0]);//pref
            int M = int.Parse(temp_d[1]);//city
            int[] P = new int[M];
            int[] Y = new int[M];
            List<int>[] list1 = new List<int>[N];
            for(int i=0; i <= N; i++)
            {
                list1[i] = new List<int>();
            }
            for (int i = 0; i < M; i++)
            {
                string[] temp = Console.ReadLine().Split(' ');
                P[i] = int.Parse(temp[0]);
                Y[i] = int.Parse(temp[1]);
                //if(list1[P[i]]==null) list1[P[i]] = new List<int>();
                list1[P[i]].Add(Y[i]);
            }
            for (int i = 0; i <= N; i++)
            {
                if(list1[i]!=null) list1[i].Sort();
            }
            for (int i = 0; i < M; i++)
            {
                Console.WriteLine("{0:d12}", P[i]*1000000+ list1[P[i]].IndexOf(Y[i]) + 1);
            }
            
        }
    }