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.*;

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, Integer> h = new HashMap<>();
        List<City> city = new ArrayList<>();
        for (int i = 0; i < m; i++) {
            int Pref = Integer.parseInt(sc.next());
            int Year = Integer.parseInt(sc.next());
            city.add(new City(i, Pref, Year));
            if (h.containsKey(Pref)) {
                h.put(Pref, h.get(Pref) + 1);
            } else {
                h.put(Pref, 1);
            }
        }
        sc.close();
        city.sort((o1, o2) -> Integer.compare(o2.Year, o1.Year));
        for (City c : city) {
            c.Num = h.get(c.Pref);
            h.put(c.Pref, h.get(c.Pref) - 1);
        }
        city.sort((o1, o2) -> Integer.compare(o1.ID, o2.ID));
        for (City c : city) {
            System.out.printf("%06d%06d\n", c.Pref, c.Num);
        }
    }

    static class City {
        int ID;
        int Pref;
        int Year;
        int Num;

        City(int ID, int Pref, int Year) {
            this.ID = ID;
            this.Pref = Pref;
            this.Year = Year;
            this.Num = 0;
        }
    }
}