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[] P = new int[M];
		int[] Y = new int[M];
		int[] num = new int[M];
		List<List<Integer>> number = new ArrayList<>();
		List<List<Integer>> answer = new ArrayList<>();
		for(int i=0; i<N; i++){
			number.add(new ArrayList<Integer>());
			answer.add(new ArrayList<Integer>());
		}
		for(int i=0; i<M; i++){
			P[i] = sc.nextInt()-1;
			Y[i] = sc.nextInt()-1;
			num[i] = number.get(P[i]).size();
			number.get(P[i]).add(Y[i]);
		}
		for(int i=0; i<N; i++){
			for(int j=0,l=number.get(i).size(); j<l; j++){
				int min = 0;
				for(int k=1,m=number.get(i).size()/*l-j*/; k<m; k++){
					if(number.get(i).get(k) < number.get(i).get(min)){
						min = k;
					}
				}
				answer.get(i).add(min+j);
				number.get(i).remove(min);
			}
		}
		for(int i=0; i<M; i++){
			System.out.printf("%06d%06d\n", P[i]+1, answer.get(P[i]).get(num[i])+1);
		}
		return;
	}
}