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: Accepted)

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.Comparator;
import java.util.PriorityQueue;
public class Main {
	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] inputs;
		inputs = br.readLine().split(" ");
		int n = Integer.parseInt(inputs[0]); // 県の個数
		int m = Integer.parseInt(inputs[1]); // 市の個数

		// 県、年でソート
		PriorityQueue<City> city = new PriorityQueue<>(m, new Comparator<City>() {
			@Override
			public int compare(City o1, City o2) {
				if ( o1.pref != o2.pref ) {		// 県でソート
					return o1.pref - o2.pref;
				} else {						// 同じ県の時は年でソート
					return o1.year - o2.year;
				}
			}
		});
		for ( int id = 1; id <= m; id++ ) {
			inputs = br.readLine().split(" ");
			city.add(new City(id, Integer.parseInt(inputs[0]), Integer.parseInt(inputs[1])));
		}

		// 県ごとに年でナンバー付けしてidでソート
		PriorityQueue<City> city2 = new PriorityQueue<>(m, new Comparator<City>() {
			@Override
			public int compare(City o1, City o2) {
				return o1.id - o2.id;
			}
		});
		int p = 0;
		int num = 0;
		while ( city.size() > 0 ) {
			City c = city.poll();
			// 新出の県の場合
			if ( p != c.pref ) {
				p = c.pref;
				num = 1;
			} else {
				num++;
			}

			c.num = num;
			city2.add(c);
			// System.out.println("id:" + c.id + " pref:" + c.pref + " year:" + c.year);
		}

		PrintWriter pw = new PrintWriter(System.out);
		while ( city2.size() > 0 ) {
			City c = city2.poll();
			// System.out.println("id:" + c.id + " pref:" + c.pref + " num:" + c.num);
			pw.print(String.format("%06d", c.pref));
			pw.println(String.format("%06d", c.num));
		}
		pw.flush();
		br.close();
	}
}

class City {
	int	id		= 0;
	int	pref	= 0;
	int	year	= 0;
	int	num		= 0;

	public City(int id, int pref, int year) {
		this.id = id;
		this.pref = pref;
		this.year = year;
	}
}