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.Arrays;
import java.util.HashMap;
import java.util.Map.Entry;
import java.util.Scanner;
import java.util.TreeMap;

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];

		String s[] = new String[m];

		HashMap<Integer, TreeMap<Integer, Integer>> map = new HashMap<>();

		for (int i = 0; i < m; i++) {
			p[i] = sc.nextInt();
			y[i] = sc.nextInt();

			map.computeIfAbsent(p[i], e -> new TreeMap<>()).put(y[i], i);

		}

		for (Entry<Integer, TreeMap<Integer, Integer>> a : map.entrySet()) {
			int i = 0;
			for (Entry<Integer, Integer> b : a.getValue().entrySet()) {

				String s1 = String.format("%06d", a.getKey());
				String s2 = String.format("%06d", ++i);
				s[b.getValue()] = s1 + s2;

			}

		}

		Arrays.stream(s).forEach(System.out::println);

		sc.close();

	}

}