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.*;

class City implements Comparable<City>{
	final int prefecture;
	private final int year;

	City(int prefecture, int year){
		this.prefecture = prefecture;
		this.year = year;
	}

	String toString(int number){
		return String.format("%06d%06d", prefecture, number);
	}

	@Override
	public int compareTo(City o) {
		return Comparator.<City>comparingInt(t -> t.year).compare(this, o);
	}
}

class Solver {
	static final Solver INSTANCE = new Solver();

	void solve(Scanner sc) {
		int N = sc.nextInt();
		int M = sc.nextInt();
		PriorityQueue<City> cities = new PriorityQueue<>(N);
		for (int i = 0; i < M; i++) {
			int P = sc.nextInt();
			int Y = sc.nextInt();
			cities.add(new City(P, Y));
		}

		int[] prefecturesCounter = new int[N];
		StringJoiner joiner = new StringJoiner("\n");
		while (!cities.isEmpty()){
			City city = cities.remove();
			joiner.add(city.toString(prefecturesCounter[city.prefecture - 1]++ + 1));
		}
		System.out.println(joiner.toString());
	}
}

class Main {
	public static void main(String... args) {
		Scanner in = new Scanner(System.in);

		Solver.INSTANCE.solve(in);

		in.close();
	}
}