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: Time Limit Exceeded)

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

namespace ABC113_C
{
    public class Program

    {

        public  struct City
        {
            public int index { get; set; }
            public int year { get; set; } 
            public int p { get; set; }
            public int BirthOrder { get; set; }

            public City(int i,int year,int p)
            {
                this.index = i;
                this.year = year;
                this.p = p;
                this.BirthOrder = 0;
            }
            public void setBirthOrder(int i)
            {
                this.BirthOrder = i;
            }

        }

        public static void Main(string[] args)
        {
            int[] line = ReadIntAr();
            int n = line[0];
            int m = line[1];

            Dictionary<int,City> cities = new Dictionary<int,City>();
            int[] tmp;
            for (int i = 0 ; i < m ; i++)
            {
                tmp = ReadIntAr();
                cities.Add(i,new City(i,tmp[1],tmp[0]));
            }

            for (int j = 1 ; j <= n ; j++)
            {

                var tmp2 = cities.Where(x => x.Value.p == j).OrderBy(x => x.Value.year);
                int k = 1;
                foreach (var item in tmp2)
                {
                    City tmpcity = cities[item.Key];
                    tmpcity.BirthOrder = k;
                    cities[item.Key] = tmpcity;
                    k++;
                }
            }

            var res = cities.OrderBy(x => x.Key).ToArray();
            for (int i = 0 ; i < m ; i++)
            {
                Console.WriteLine(res[i].Value.p.ToString("000000") + res[i].Value.BirthOrder.ToString("000000"));
            }
            
        }

        static string ReadSt() { return Console.ReadLine(); }
        static int ReadInt() { return int.Parse(Console.ReadLine()); }
        static long ReadLong() { return long.Parse(Console.ReadLine()); }
        static double ReadDouble() { return double.Parse(Console.ReadLine()); }
        static string[] ReadStAr(char sep = ' ') { return Console.ReadLine().Split(sep); }
        static int[] ReadIntAr(char sep = ' ') { return Array.ConvertAll(Console.ReadLine().Split(sep), e => int.Parse(e)); }
        static long[] ReadLongAr(char sep = ' ') { return Array.ConvertAll(Console.ReadLine().Split(sep), e => long.Parse(e)); }
        static double[] ReadDoubleAr(char sep = ' ') { return Array.ConvertAll(Console.ReadLine().Split(sep), e => double.Parse(e)); }

    }

}