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.*;

public class Main {
    public static void main(String[] args) throws Exception{
        Scanner sc = new Scanner(System.in);

        int N = sc.nextInt();
        int M = sc.nextInt();
        List<TreeMap> mapList = new ArrayList<TreeMap>();
        int[][] valAry = new int[M][2];

        for(int i = 0; i < N ; i++){
            TreeMap<Integer, Integer> map = new TreeMap<Integer, Integer>();
            mapList.add(map);
        }
        for(int i = 0; i < M ; i++){
            int P = sc.nextInt();
            int Y = sc.nextInt();
            mapList.get(P-1).put(Y, i);
            valAry[i][0] = P;
            valAry[i][1] = Y;
        }
        for(Map map : mapList){
            Iterator<Map.Entry<Object, Object>> it = map.entrySet().iterator();
            int i = 1;
            while (it.hasNext()) {
                Map.Entry<Object, Object> entry = it.next();
                entry.setValue(i);
                i++;
            }
            System.out.println();
        }
        for(int i = 0; i < M ; i++){
            System.out.println(format(valAry[i][0])+format((int) mapList.get(valAry[i][0]-1).get(valAry[i][1])));
        }

    }

    public static String format(int val){
        if(val > 99999) return "" + val;
        else if(val > 9999) return "0" + val;
        else if(val > 999) return "00" + val;
        else if(val > 99) return "000" + val;
        else if(val > 9) return "0000" + val;
        else if(val > 0) return "00000" + val;
        else return "";
    }
}