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.Linq;
using System.IO;
using System.Collections.Generic;
using System.Text;
using System.Threading.Tasks;

namespace AtCoder {
    public class Program {
        public static void Main() {
            string[] Keys = Console.ReadLine().Split(' ');
            int N = int.Parse(Keys[0]);
            int M = int.Parse(Keys[1]);
            City[] cities = new City[M];
            for (int i = 0; i < M; i++) {
                Keys = Console.ReadLine().Split(' ');
                cities[i] = new City(int.Parse(Keys[0]), int.Parse(Keys[1]), i);
            }
            cities = cities.OrderBy(c => c.Year).ToArray();
            int[] Count = new int[N];
            for (int i = 0; i < M; i++) {
                cities[i].Generate(Count[cities[i].Prefacture] + 1);
                Count[cities[i].Prefacture]++;
            }
            cities = cities.OrderBy(c => c.No).ToArray();
            for (int i = 0; i < M; i++) {
                Console.WriteLine(cities[i].Code);
            }
        }
    }

    public class City {
        public int Prefacture;
        public int Year;
        public int No;
        public string Code;
        public City(int P,int Y,int N) {
            Prefacture = P;
            Year = Y;
            No = N;
        }
        public void Generate(int i) {
            Code = Prefacture.ToString("000000") + i.ToString("000000");
        }
    }
}