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.util.*;
public class Main {

  public static void main(String[] args) { 
      Scanner sc = new Scanner(System.in);
      int n = sc.nextInt();
      int m = sc.nextInt();

      Map<Integer, ArrayList<int[]>> ps = new HashMap<>();

      for(int i = 1; i <= m; i++) {
        int pNum = sc.nextInt();
        int year = sc.nextInt();
        if(!ps.containsKey(pNum))
          ps.put(pNum, new ArrayList<>());
        ps.get(pNum).add(new int[]{year, i});
      }
          
      for(ArrayList<int[]> pp : ps.values()) {
        Collections.sort(pp, (a, b) -> a[0] - b[0]);
      }

      String[] cities = new String[m+1];
      for(Map.Entry<Integer, ArrayList<int[]>> entry : ps.entrySet()) {
        ArrayList<int[]> pp = entry.getValue();
        
        for(int k = 0; k < pp.size(); k++) {
            
          StringBuilder sb = new StringBuilder();
          String pStr = String.valueOf(entry.getKey());
          for(int j = 0; j < 6 - pStr.length(); j++)
            sb.append("0");
          sb.append(pStr);

          pStr = String.valueOf(k+1);
          for(int j = 0; j < 6 - pStr.length(); j++)
            sb.append("0");
          sb.append(k+1);

          cities[pp.get(k)[1]] = sb.toString();
        }
      }
      
      for(int i = 1; i < cities.length; i++)
       System.out.println(cities[i]);
  }
}