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 Java (OpenJDK 11.0.6) (judge verdict: Accepted)

import java.util.*;

class City {
	public int no;
	public String id;
	public int pref;
	public long year;

	public City(int no, int pref, long year) {
		this.no = no;
		this.pref = pref;
		this.year = year;
	}
}

class CityComparator implements Comparator<City> {
	@Override
	public int compare(City c1, City c2) {
		if (c1.pref != c2.pref) {
			return c1.pref < c2.pref ? -1 : 1;
		} else {
			return c1.year < c2.year ? -1 : 1;
		}
	}
}

class CityResetComparator implements Comparator<City> {
	@Override
	public int compare(City c1, City c2) {
		return c1.no < c2.no ? -1 : 1;
	}
}

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int M = sc.nextInt();
		List<City> cities = new ArrayList<City>();
		for (int i = 0; i < M; i++) {
			int pref = sc.nextInt();
			long year = sc.nextLong();
			cities.add(new City(i, pref, year));
		}

		// sort
		Collections.sort(cities, new CityComparator());
		int[] prefCnt = new int[N + 1];
		Arrays.fill(prefCnt, 1);

		for (City city : cities) {
			// create identifier id
			city.id = paddingZero(city.pref) + paddingZero(prefCnt[city.pref]);
			prefCnt[city.pref]++;
		}

		// re-sort
		Collections.sort(cities, new CityResetComparator());

		for (City city : cities) {
			System.out.println(city.id);
		}

		sc.close();
	}

	public static String paddingZero(int val) {
		String str = String.valueOf(val);
		String paddingStr = String.format("%6s", str).replace(" ", "0");
    return paddingStr;
	}
}