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)

/*
 * AtCoder Beginner Contest 113
 * https://beta.atcoder.jp/contests/abc113
 * C - ID
 */

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

namespace ConsoleApplication1{

    class CityInfo {
        private readonly Dictionary<string, List<string>> cities = new Dictionary<string, List<string>>();

        //情報を追加する
        public void SetCityInfo(string p, string y) {

            if(!cities.ContainsKey(p)) {
                cities.Add(p, new List<string>());
            }

            cities[p].Add(y);
        }
        
        //IDを返す
        public string GetCityId(string p, string y) {
            var sortedList = cities[p].OrderBy(year =>int.Parse(year));
            var index = 1;
            foreach (var val in sortedList) {
                if (val == y) {
                    break;
                }
                index++;
            }
            return $"{p.PadLeft(6, '0')}{index:D6}";
        }
    }
                
    
    internal class Program{
        
        public static int Main(string[] args) {
            var tmp = Console.ReadLine().Trim().Split();
            var n = int.Parse(tmp[0]);
            var m = int.Parse(tmp[1]);
            
            var cityInfo = new CityInfo();
            var p_array = new string[m];
            var y_array = new string[m];
            
            for (int i = 0; i < m; i++) {
                var data = Console.ReadLine().Trim().Split();
                p_array[i] = data[0];
                y_array[i] = data[1];
                cityInfo.SetCityInfo(p_array[i], y_array[i]);
            }

            for (int i = 0; i < m; i++) {
                Console.WriteLine(cityInfo.GetCityId(p_array[i], y_array[i]));
            }
            
            return 0;
        }
    }
}