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 Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import java.util.Scanner;
import java.util.stream.Collectors;

public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int n = scan.nextInt();
        int m = scan.nextInt();

        List<City> list = new ArrayList<>();
        for(int i = 0; i < m; i++) {
        	list.add(new City(i, scan.nextInt(), scan.nextInt()));
        }
        list = list.stream().sorted(new Comparator<City>() {
        	public int compare(City c1, City c2) {
        		return c1.prefecture.compareTo(c2.prefecture);
        	}
        }).collect(Collectors.toList());

        list = list.stream().sorted(new Comparator<City>() {
        	public int compare(City c1, City c2) {
        		return c1.year.compareTo(c2.year);
        	}
        }).collect(Collectors.toList());

        int wkPrefecture = list.get(0).prefecture;
        int wkId = 1;
        for(int i = 0; i < list.size(); i++) {
        	if(list.get(i).prefecture == wkPrefecture) {
        		list.get(i).ID = String.format("%06d", list.get(i).prefecture) + String.format("%06d", wkId);
        		wkId++;
        	}else {
        		wkId = 1;
        		wkPrefecture = list.get(i).prefecture;
        		list.get(i).ID = String.format("%06d", list.get(i).prefecture) + String.format("%06d", wkId);
        	}
        }
        list = list.stream().sorted(new Comparator<City>() {
        	public int compare(City c1, City c2) {
        		return c1.index.compareTo(c2.index);
        	}
        }).collect(Collectors.toList());

        for(int i = 0; i < list.size(); i++) {
        	System.out.println(list.get(i).ID);
        }
    }
}

class City {
	Integer index;
	Integer prefecture;
	Integer year;
	String ID = "";
	City(int index, int prefecture, int year){
		this.index = index;
		this.prefecture = prefecture;
		this.year = year;
	}
}