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.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
// import java.io.PrintWriter;
import java.util.Arrays;
import java.util.Comparator;

public class Main {

  public static void main(String[] args) {
    new Main().run();
  }

  public void run() {

    try(BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        ) {

      String[] lns = in.readLine().split(" ");
      int n = Integer.parseInt(lns[0]);
      int m = Integer.parseInt(lns[1]);
      City[] city = new City[m];
      City[] city2 = new City[m];
      int[] pref = new int[n+1];

      int x,y;
      for(int i=0; i<m; i++) {
        lns = in.readLine().split(" ");
        x = Integer.parseInt(lns[0]);
        y = Integer.parseInt(lns[1]);
        city2[i] = city[i] = new City(i, x, y);
      }

      Arrays.parallelSort(city2, new Comparator<City>() {
        public int compare(City a, City b) {
          if(a.y == b.y) return 0;
          return a.y > b.y ? 1 : -1;
        }
      });

      for (City c : city2)
        c.no = ++pref[c.p];

      // String no;
      StringBuilder buf = new StringBuilder();
      String[] pre0 = {"000000","00000","0000","000","00","0",""};
      for(int i=0, p, no; i<m; i++) {
        // no = String.format("%06d%06d", city[i].p,city[i].no);
        p  = city[i].p;
        no = city[i].no;
        buf.append(pre0[len(p)])
           .append(p)
           .append(pre0[len(no)])
           .append(no)
           .append('\n');
        // out.println(no);
      }
      // out.flush();
      System.out.print(buf);
    }
    catch(IOException e) {
      System.err.println(e);
    }
  }

  int len(int n) {
    int i=1;
    for(int j=10; ; i++, j*=10)
      if(n<j) break;
    return i;
  }
  class City {
    int s;
    int p;
    int y;
    int no;

    public City(int s, int p, int y) {
      this.s = s;
      this.p = p;
      this.y = y;
    }
  }
}