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.io.PrintWriter;
import java.util.Map;
import java.util.Scanner;
import java.util.TreeMap;

public class Main {

    public static void main(String[] args) {
        try (
                Scanner in = new Scanner(System.in);
                PrintWriter out = new PrintWriter(System.out))
        {
            final int N = in.nextInt();
            final int M = in.nextInt();

            final int[] P = new int[M];
            final int[] Y = new int[M];
            Map<Integer, Integer> yearIdxMap = new TreeMap<>();
            for (int i = 0; i < M; ++i) {
                P[i] = in.nextInt();
                Y[i] = in.nextInt();
                yearIdxMap.put(Y[i], i);
            }

            final String[] cityId = new String[M];
            final int[] seq = new int[N];
            for (int year : yearIdxMap.keySet()) {
                int i = yearIdxMap.get(year);
                cityId[i] = String.format("%06d%06d", P[i], ++seq[P[i] - 1]);
            }

            for (int i = 0; i < M; ++i) {
                out.println(cityId[i]);
            }
        }
    }
}