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 Scala (2.11.7) (judge verdict: Time Limit Exceeded)

import java.util.Scanner

import scala.annotation.tailrec
import scala.collection.mutable

object Main extends App {
  type City = (Int, Int)
  val sc = new Scanner(System.in)
  val N, M = sc.next.toInt
  val map = Array.fill(N)(Vector.empty[Int])
  val seq = mutable.ListBuffer.empty[City]
  (0 until M).foreach { _ =>
    val city = (sc.next.toInt, sc.next.toInt)
    seq.append(city)
    map.update(city._1 - 1, city._2 +: map(city._1 - 1))
  }
  (0 until N).foreach { i => map.update(i, map(i).sorted) }

  seq.foreach { city =>
    val ys = map(city._1 - 1)
    val rank = find(ys, city._2, 0, ys.size - 1) + 1
    println("%06d%06d".format(city._1, rank))
  }

  @tailrec def find(xs: Vector[Int], value: Int, min: Int, max: Int): Int = {
    val idx = (max + min) / 2
    val v = xs(idx)
    if (v == value) {
      idx
    } else if (v < value) {
      find(xs, value, idx + 1, max)
    } else {
      find(xs, value, min, idx - 1)
    }
  }
}