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();

        Map<Integer, List<Integer>> map = new HashMap<>();
        int[] parr = new int[m];
        int[] yarr = new int[m];
        for(int i = 0; i < m;i++){
            int p = sc.nextInt();
            parr[i] = p;
            int y = sc.nextInt();
            yarr[i] = y;

            if(map.containsKey(p)){
                map.get(p).add(y);
            } else {
                List<Integer> list = new ArrayList<>();
                list.add(y);
                map.put(p, list);
            }
        }

        Map<Integer, Map<Integer, Integer>> ansmap = new HashMap<>();
        for(int key : map.keySet()){
            List<Integer> list = map.get(key);
            Collections.sort(list);
            Map<Integer, Integer> tmpmap = new HashMap<>();
            for(int i = 0; i < list.size();i++){
                tmpmap.put(list.get(i), i+1);
            }
            ansmap.put(key, tmpmap);
        }

        for(int i = 0; i < m;i++){
            int index = ansmap.get(parr[i]).get(yarr[i]);
            System.out.printf("%06d%06d\n", parr[i], index);
        }
    }

}