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: Accepted)

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

public class Main implements Runnable {

    private static Scanner sc = new Scanner(System.in);

    public static void main(String[] args) {
        new Thread(null, new Main(), "", 128 * 1024 * 1024).start();
    }

    public void run() {
        int N = sc.nextInt(), M = sc.nextInt();
        City[] cities = new City[M];
        for (int i = 0; i < M; i++) {
            cities[i] = (new City(i, sc.nextInt(), sc.nextInt()));
        }
        Arrays.sort(cities, Comparator.comparingInt(city -> city.year));
        String[] ans = new String[M];
        int[] count = new int[N + 1];
        for (int i = 0; i < M; i++) {
            count[cities[i].pref]++;
            ans[cities[i].order] = String.format("%06d", cities[i].pref) + String.format("%06d", count[cities[i].pref]);
        }
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < M; i++) {
            sb.append(ans[i]).append("\n");
        }
        System.out.print(sb);
    }

    class City {

        int order, pref, year;

        public City(int order, int pref, int year) {
            this.order = order;
            this.pref = pref;
            this.year = year;
        }
    }
}