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.Scanner;

public class Main {

    public static void main(String[] args) {
        final Scanner scanner = new Scanner(System.in);
        final int n = scanner.nextInt();
        final int m = scanner.nextInt();

        // index(0-origin), prefecture(1-origin), year, order(1-origin)
        int[][] cities = new int[m][4];
        for (int i = 0; i < m; i++) {
            int prefecture = scanner.nextInt();
            int year = scanner.nextInt();
            cities[i] = new int[]{i, prefecture, year, 0};
        }
        Arrays.sort(cities, (a, b) -> (a[1] == b[1]) ? a[2] - b[2] : a[1] - b[1]);

        cities[0][3] = 1;
        int order = 1;
        for (int i = 1; i < m; i++) {
            if (cities[i - 1][1] != cities[i][1]) {
                cities[i][3] = 1;
                order = 1;
            } else {
                cities[i][3] = ++order;
            }
        }

        Arrays.sort(cities, Comparator.comparingInt(a -> a[0]));
        for (int i = 0; i < m; i++) {
            System.out.println(String.format("%06d", cities[i][1]) + String.format("%06d", cities[i][3]));
        }
    }
}