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 Java (OpenJDK 11.0.6) (judge verdict: Accepted)

import java.util.*;

public class Main {

    public static void main(String args[]) {

        // 入力
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int m = Integer.parseInt(sc.next());
        Integer[] p = new Integer[m];
        Integer[] y = new Integer[m];
        Map<Integer, PriorityQueue<Integer>> map = new HashMap<>();
        for (int i = 1; i <= n; i++) {
            map.put(i, new PriorityQueue<Integer>());
        }
        for (int i = 0; i < m; i++) {
            p[i] = Integer.parseInt(sc.next());
            y[i] = Integer.parseInt(sc.next());
            map.get(p[i]).add(y[i]);
        }
        sc.close();

        // 主処理
        Map<Integer, Integer> birthNumberMap = new HashMap<>();
        for (int i = 1; i <= n; i++) {
            int num = 1;
            while (!map.get(i).isEmpty()) {
                birthNumberMap.put(map.get(i).poll(), num);
                num++;
            }
        }

        List<String> list = new ArrayList<>();
        for (int i = 0; i < m; i++) {
            String left = String.format("%06d", p[i]);
            String right = String.format("%06d", birthNumberMap.get(y[i]));
            list.add(left + right);
        }

        String result = String.join("\r\n", list);

        // 出力
        System.out.println(result);
    }
}