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 {

  static Scanner sc = new Scanner(System.in);

  public static void main(String[] args) {

    int N = sc.nextInt();
    int M = sc.nextInt();

    ArrayList<City> cities = new ArrayList();
    for (int i=0; i<M; i++) {
      cities.add(new City(i, sc.nextInt(), sc.nextInt()));
    }

    cities.sort((x, y) -> {
      if (x.p == y.p) {
        return x.y - y.y;
      } else {
        return x.p - y.p;
      }
    });

    String[] ids = new String[M];

    int count = 0;
    for (int i=0; i<M; i++) {
      City c = cities.get(i);
      if (i == 0 || c.p != cities.get(i-1).p) count = 0;
      else count++;
      ids[c.i] = padding0(c.p, 6) + padding0(count+1, 6);
    }

    for (int i=0; i<M; i++) {
      System.out.println(ids[i]);
    }

  }

  static String padding0(int n, int m) {
    String s = Integer.toString(n);
    while (m - s.length() > 0) s = "0" + s;
    return s;
  }


  static class City {
    int i, p, y;
    City (int i, int p, int y) {
      this.i = i;
      this.p = p;
      this.y = y;
    }
  }

}