Problem:
Score: 100 points

Problem Statement

There is a train going from Station A to Station B that costs X yen (the currency of Japan).

Also, there is a bus going from Station B to Station C that costs Y yen.

Joisino got a special ticket. With this ticket, she can take the bus for half the fare if she travels from Station A to Station B by train and then travels from Station B to Station C by bus.

How much does it cost to travel from Station A to Station C if she uses this ticket?

Constraints

1 \leq X,Y \leq 100

Y is an even number.

All values in input are integers.

Input

Input is given from Standard Input in the following format:

X Y

Output

If it costs x yen to travel from Station A to Station C, print x.

Sample Input 1

81 58

Sample Output 1

110

The train fare is 81 yen.

The train fare is 58 ⁄ 2=29 yen with the 50% discount.

Thus, it costs 110 yen to travel from Station A to Station C.

Sample Input 2

4 54

Sample Output 2

31

Solution in Scala (2.11.7) (judge verdict: Runtime Error)

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 = Integer.parseInt(sc.next)
  val map = Array.fill(N)(Vector.empty[Int])
  val seq = mutable.ListBuffer.empty[City]
  (0 until M).foreach { _ =>
    val city = (Integer.parseInt(sc.next), Integer.parseInt(sc.next))
    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)
    }
  }
}