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.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Scanner;

public class Main
{
    public static void main(String[] args)
    {
        final Scanner sc = new Scanner(System.in);
        final int N = sc.nextInt();
        final int M = sc.nextInt();
        final int[] P = new int[M];
        final int[] Y = new int[M];
        final Map<Integer, List<Integer>> areaToYears = new HashMap<Integer, List<Integer>>();
        List<Integer> tempList;
        for (int i = 0; i < M; i++)
        {
            P[i] = sc.nextInt();
            Y[i] = sc.nextInt();
            if (areaToYears.containsKey(P[i]))
            {
                areaToYears.get(P[i]).add(Y[i]);
            } else
            {
                tempList = new ArrayList<Integer>();
                tempList.add(Y[i]);
                areaToYears.put(P[i], tempList);
            }
        }

        for (final Entry<Integer, List<Integer>> entry : areaToYears.entrySet())
        {
            Collections.sort(entry.getValue());
        }
        String tempArea;
        String tempYearOrder;
        for (int i = 0; i < M; i++)
        {
            tempArea = String.valueOf(P[i]);
            while (tempArea.length() < 6)
            {
                tempArea = "0" + tempArea;
            }
            tempYearOrder = String.valueOf(areaToYears.get(P[i]).indexOf(Y[i]) + 1);
            while (tempYearOrder.length() < 6)
            {
                tempYearOrder = "0" + tempYearOrder;
            }
            System.out.println(tempArea + tempYearOrder);
        }
    }
}