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.Comparator;
import java.util.TreeSet;
import java.util.stream.Collectors;

public class Main {
    private static java.util.Scanner scanner = new java.util.Scanner(System.in);

    public static void main(String[] args) {
        int n = scanner.nextInt(), m = scanner.nextInt();
        City[] cities = new City[m];
        for (int i = 0; i < m; i++)
            cities[i] = new City(scanner.nextInt(), scanner.nextInt());
        Arrays.stream(cities)
                .collect(Collectors.groupingBy(city -> city.p, Collectors.toCollection(() -> new TreeSet<>(Comparator.comparingInt(city -> city.y)))))
                .values()
                .forEach(cityList -> {
                    int i = 0;
                    for (City city : cityList)
                        city.o = ++i;
                });
        for (City city : cities)
            System.out.println(String.format("%06d%06d", city.p, city.o));
    }

    static class City {
        int p, y, o;

        City(int p, int y) {
            this.p = p;
            this.y = y;
        }
    }
}