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: Time Limit Exceeded)

import java.util.Arrays;
import java.util.Scanner;

// Java8
public class Main {
	Scanner sc = new Scanner(System.in);

	public static void main(String[] args) throws Exception {
		new Main().run();
	}

	void run() throws Exception {
		int n = sc.nextInt();
		int m = sc.nextInt();

		Hoge[] ds = new Hoge[m];
		Hoge[] cl = new Hoge[m];
		
		for(int i=0; i<m; i++) {
			int p = sc.nextInt();
			int y = sc.nextInt();
			ds[i] = cl[i] = new Hoge(p, y);
		}
		Arrays.sort(cl);

		int id = 0;
		for(int i=0; i<m; i++) {
			if(i==0 || cl[i].pref != cl[i-1].pref) id = 0;
			cl[i].setId(++id);
		}
		
		for(int i=0; i<m; i++) System.out.println(ds[i]);
	}
}
class Hoge implements Comparable<Hoge>{
	int pref;
	int year;
	int id;

	Hoge(int p, int y) {
		pref = p;
		year = y;
	}
	
	@Override
	public int compareTo(Hoge o)
	{
		return pref<o.pref ? 1 : pref>o.pref ? -1 : Integer.compare(year, o.year);
	}

	public void setId(int id)
	{
		this.id = id;
	}
	
	@Override
	public String toString()
	{
		return String.format("%06d%06d", pref, id);
	}
}