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.*;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int m = sc.nextInt();
        int[] p = new int[m];
        int[] y = new int[m];
        HashMap<Integer, PriorityQueue<Integer>> map = new HashMap<>();
        
        for(int i = 0; i < m; i++) {
            int pNum = sc.nextInt();
            int yNum = sc.nextInt();
            p[i] = pNum;
            y[i] = yNum;
            if(map.containsKey(pNum)) {
                map.get(pNum).add(yNum);
            } else {
                PriorityQueue<Integer> pq = new PriorityQueue<>();
                pq.add(yNum);
                map.put(pNum, pq);
            }
        }
        HashMap<Integer, HashMap<Integer, Integer>> data = new HashMap<>();
        for(Map.Entry<Integer, PriorityQueue<Integer>> entry: map.entrySet()) {
            int prefecture = entry.getKey();
            int counter = 1;
            HashMap<Integer, Integer> order = new HashMap<>();
            PriorityQueue<Integer> queue = entry.getValue();
            while(!queue.isEmpty()) {
                order.put(queue.poll(), counter);
                counter++;
            }
            data.put(prefecture, order);
        }
        for(int i = 0; i < m; i++) {
            System.out.print(String.format("%06d", p[i]));
            System.out.println(String.format("%06d", data.get(p[i]).get(y[i])));
        }
    }
}