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.*;
import java.lang.*;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int m = sc.nextInt();
		int[] p = new int[m];
		ArrayList<City> city = new ArrayList<>(m);
		for (int i = 0; i < m; i++) {
			p[i] = sc.nextInt();
			city.add(new City(i, sc.nextInt()));
		}
		Collections.sort(city, new CityComparator());
		String[] ans = new String[m];
		int[] count = new int[n];
		for (int i = 0; i < m; i++) {
			City tmp = city.get(i);
			StringBuilder id = new StringBuilder();
			count[p[tmp.number] - 1]++;
			id.append(p[tmp.number] * 1000000 + count[p[tmp.number] - 1]);
			while (id.length() < 12) {
				id.insert(0, "0");
			}
			ans[tmp.number] = String.valueOf(id);
		}
		for (int i = 0; i < m; i++) {
			System.out.println(ans[i]);
		}
	}
}

class City {
	int number;
	int year;

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

class CityComparator implements Comparator<City> {
	@Override
	public int compare(City c1, City c2) {
		return c1.year - c2.year;
	}
}