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)

// https://beta.atcoder.jp/contests/abc113/submissions/3538151
import java.io.File;
import java.io.IOException;
import java.util.*;
 
public class Main {
 
	public static void main(String[] args) throws IOException {
		//File file = new File("input.txt");
		//Scanner sc = new Scanner(file);
		
		Scanner sc = new Scanner(System.in);
		
		int N = sc.nextInt();
		int M = sc.nextInt();
		
		ArrayList<ArrayList<Info>> list = new ArrayList<ArrayList<Info>>();
		for(int i = 0; i < N; i++) list.add(new ArrayList<Info>());
		
		for(int i = 0; i < M; i++){
			int index = i;
			int P = sc.nextInt();
			int Y = sc.nextInt();
			Info f = new Info();
			f.index = i;
			f.year = Y;
			list.get(P-1).add(f);
		}
		
		for(int i = 0; i < N; i++) Collections.sort(list.get(i), new yearComparator());
		
		ArrayList<Info> ansList = new ArrayList<Info>();
		for(int i = 0; i < N; i++){
			ArrayList<Info> pList = list.get(i);
			for(int j = 0; j < pList.size(); j++){
				Info f = pList.get(j);
				String number = String.format("%06d%06d", (i + 1), (j + 1));
				f.number = number;
				ansList.add(f);
			}
		}
		
		Collections.sort(ansList, new indexComparator());
		
		for(Info f : ansList){
			System.out.println(f.number);
		}
		
		/*
		for(int i = 0; i < N; i++){
			for(Info f : list.get(i)){
				System.out.println(f.index + " " + f.year + " " + f.number);
			}
		}
		*/
	}
	
	public static class yearComparator implements Comparator<Info> {
		@Override
		public int compare(Info info1, Info info2) {
			return info1.year < info2.year ? -1 : 1;
		}
	}
	
	public static class indexComparator implements Comparator<Info> {
		@Override
		public int compare(Info info1, Info info2) {
			return info1.index < info2.index ? -1 : 1;
		}
	}
	
	public static class Info{
		int index = 0;
		int year = 0;
		String number = "";
	}
}