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: Time Limit Exceeded)

import java.util.HashMap;
import java.util.LinkedList;
import java.util.Map;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int M = sc.nextInt();
		int[][] input = new int[M][2];
		for(int i = 0;i < M;++i) {
			input[i][0] = sc.nextInt();
			input[i][1] = sc.nextInt();
		}
		sc.close();
		
		Map<Integer, LinkedList<Integer>> map = new HashMap<>();
		for(int i = 0;i < M;++i) {
			if(!map.containsKey(input[i][0])) {
				LinkedList<Integer> cap = new LinkedList<>();
				cap.add(i);
				map.put(input[i][0], cap);
			}else {
				LinkedList<Integer> list = map.get(input[i][0]);
				int left = 0, right = list.size();
				while(left <= right) {
					int j = (left + right)/2;
					if(input[list.get(j)][1] < input[i][1]) {
						if(j+1 > list.size()-1) {
							list.add(i);
							break;
						}else if(input[list.get(j+1)][1] > input[i][1]) {
							list.add(j+1, i);
							break;
						}else {
							left = j+1;
						}
					}else {
						if(j-1 < 0) {
							list.add(0, i);
							break;
						}else if(input[list.get(j-1)][1] < input[i][1]) {
							list.add(j, i);
							break;
						}else {
							right = j-1;
						}
					}
				}
			}
		}
		
		for(Integer i : map.keySet()) {
			LinkedList<Integer> list = map.get(i);
			for(int j = 0;j < list.size();++j) {
				input[list.get(j)][1] = j;
			}
		}
		
		StringBuilder sb = new StringBuilder();
		for(int i = 0;i < M;++i)
			sb.append(String.format("%06d%06d\n", input[i][0], input[i][1]+1));
		System.out.println(sb.toString());
	}
}