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;

namespace AtCoder {

    class Program {

        static void Main(string[] args) {

            var temp = Console.ReadLine().Split(' ');
            var n = int.Parse(temp[0]);
            var m = int.Parse(temp[1]);

            var map = new List<KeyValuePair<int, int>>();

            for(int i = 0; i < m; i++) {

                var temp2 = Console.ReadLine().Split(' ');
                map.Add(new KeyValuePair<int, int>(int.Parse(temp2[0]), int.Parse(temp2[1])));
            }

            var list = new Dictionary<int , List<KeyValuePair<int, int>>>();
            foreach(var pair in map) {

                if (list.ContainsKey(pair.Key)) continue;
                list[pair.Key] = map.Where(w => w.Key == pair.Key).OrderBy(o => o.Value).ToList();
            }

            foreach (var pair in map) {

                var pref = pair.Key.ToString("D6");
                var city = (list[pair.Key].IndexOf(pair) + 1).ToString("D6");
                Console.WriteLine(pref + city);
            }
        }
    }
}