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 {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		try (Scanner sc = new Scanner(System.in)) {
			int kenCount = sc.nextInt();
			int shiCount = sc.nextInt();
			int i = 0;
			Shi[] list = new Shi[shiCount];
			// Map<Integer, TreeSet<Integer>> yearMap = new HashMap<>();
			while (i < shiCount) {
				Shi shi = new Shi();
				shi.idx = i;
				shi.ken = sc.nextInt();
				shi.year = sc.nextInt();
				list[i] = shi;
				i++;
			}

			Arrays.sort(list, (o1, o2) -> {
				if (o1.ken == o2.ken) {
					return o1.year - o2.year;
				}
				return o1.ken - o2.ken;
			});

			int[] seq = new int[kenCount + 1];
			String[] ans = new String[shiCount];
			for (int j = 0; j < shiCount; j++) {
				seq[list[j].ken]++;
				list[j].birthNum = seq[list[j].ken];
				ans[list[j].idx] = list[j].getNumberStr();
			}

			for (String a : ans) {
				System.out.println(a);
			}
		}
	}

	private static class Shi {
		private int idx = -1;
		private int ken = 0;
		private int year = 0;
		private int birthNum = -1;

		private String getNumberStr() {
			return zero(ken) + zero(birthNum);
		}

		private String zero(int num) {
			String str = String.valueOf(num);
			switch (str.length()) {
			case 1:
				return "00000" + str;
			case 2:
				return "0000" + str;
			case 3:
				return "000" + str;
			case 4:
				return "00" + str;
			case 5:
				return "0" + str;
			case 6:
				return str;
			}
			return str;
		}
	}
}