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.IOException;
import java.text.DecimalFormat;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Scanner;
public class Main {
	public static void main(String[] args) throws IOException {
		Scanner in = new Scanner(System.in);
		int n = in.nextInt(); // 県の個数
		int m = in.nextInt(); // 市の個数

		int city[][] = new int[m + 1][4]; // id, pref, year, number in pref
		for ( int id = 1; id <= m; id++ ) {
			city[id][0] = id;
			city[id][1] = in.nextInt();
			city[id][2] = in.nextInt();
		}
		Arrays.sort(city, new Comparator<int[]>() {
			@Override
			public int compare(int[] o1, int[] o2) {
				if ( o1[1] != o2[1] ) {
					return o1[1] - o2[1];	// 1.prefでソート
				} else {
					return o1[2] - o2[2];	// 2.yearでソート
				}
			}
		});

		DecimalFormat df = new DecimalFormat("000000");
		String result[] = new String[m];
		int pref = -1;
		int num = 0;
		for ( int i = 1; i <= m; i++ ) {
			if ( pref == city[i][1] ) {
				num++;
			} else {
				pref = city[i][1];
				num = 1;
			}
			result[city[i][0] - 1] = df.format(pref) + df.format(num);
		}

		StringBuilder sb = new StringBuilder();
		for ( String s : result ) {
			sb.append(s).append("\n");
		}
		System.out.println(sb.toString());
		in.close();
	}
}