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: Wrong Answer)

import java.util.*;
public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int m = sc.nextInt();
		int array[][] = new int[m][4];//pr, year, index, old
		for(int i = 0; i < m; i ++) {
			array[i][0] = sc.nextInt();
			array[i][1] = sc.nextInt();
			array[i][2] = i;
		}

		Arrays.sort(array, (a, b) -> Integer.compare(a[0], b[0]));

		int index = 0;
		for(int i = 1; i <= m; i ++) {
			if(i == m) {
				checkYear(array, index, i);
			}else if(array[i - 1][0] != array[i][0]) {
				checkYear(array, index, i);
				index = i;
			}
		}


		Arrays.sort(array, (a, b) -> Integer.compare(a[2], b[2]));
		for(int i = 0; i < m; i ++) {
			System.out.printf("%012d\n", array[i][0] * 1000000 + array[i][3]);
		}
	}

	private static void checkYear(int array[][], int index, int i) {
		for(int j = index; j < i; j ++) {
			int min = 1000000001;
			int minIndex = 0;
			for(int k = index; k < i; k ++) {
				if(array[k][3] != 0) { continue; }
				if(array[k][1] < min) {
					min = array[k][1];
					minIndex = k;
				}
			}
			array[minIndex][3] = j - index + 1;
		}
	}
}