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.io.{BufferedOutputStream, BufferedReader, InputStreamReader, PrintWriter}

import scala.collection.mutable.ArrayBuffer

object Main {
  def main(args: Array[String]): Unit = {
    val in = new BufferedReader(new InputStreamReader(System.in))
    val out = new PrintWriter(new BufferedOutputStream(System.out))

    val Array(n, m) = in.readLine().split("\\s+").map(_.toInt)
    val prefectures = Array.fill(n) {
      ArrayBuffer.empty[Int]
    }
    val cities = Array.fill(m) {
      in.readLine().split("\\s+").map(_.toInt) match {
        case Array(p, y) =>
          prefectures(p - 1) += y
          (p, y)
      }
    }

    val ids = for (p <- 0 until n) yield {
      prefectures(p).zipWithIndex.sortBy(_._1).map(_._2).zipWithIndex.sortBy(_._1).map(_._2 + 1)
    }

    val idCursors = Array.ofDim[Int](n)

    for (city <- cities) {
      val p = city._1
      out.println(f"${p}%06d${ids(p - 1)(idCursors(p - 1)) }%06d")
      idCursors(p - 1) += 1
    }

    out.flush()
  }
}