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.*;
import java.util.Map.Entry;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int n = Integer.parseInt(sc.next());
        int m = Integer.parseInt(sc.next());

        Map<Integer, List<Integer>> prefs = new HashMap<>();
        Map<Integer, Integer> yearToPref = new HashMap<>();
        List<Integer> cities = new ArrayList<>();

        for (int i = 0; i < m; i++) {
            int pref = Integer.parseInt(sc.next());
            int year = Integer.parseInt(sc.next());

            cities.add(year);
            yearToPref.put(year, pref);

            if (prefs.containsKey(pref)) {
                prefs.get(pref).add(year);
            } else {
                prefs.put(pref, new ArrayList<>(Arrays.asList(year)));
            }
        }

        prefs.forEach((pref, years) -> Collections.sort(years));

        cities.forEach(city ->
            System.out.println(
                    String.format("%06d%06d",
                            yearToPref.get(city),
                            prefs.get(yearToPref.get(city)).indexOf(city) + 1
                    ))
        );

    }
}