Problem:
Score : 400 points

Problem Statement

There is a bar of chocolate with a height of H blocks and a width of W blocks.
Snuke is dividing this bar into exactly three pieces.
He can only cut the bar along borders of blocks, and the shape of each piece must be a rectangle.

Snuke is trying to divide the bar as evenly as possible.
More specifically, he is trying to minimize S_{max} - S_{min}, where S_{max} is the area (the number of blocks contained) of the largest piece, and S_{min} is the area of the smallest piece.
Find the minimum possible value of S_{max} - S_{min}.

Constraints

2 ≤ H, W ≤ 10^5

Input

Input is given from Standard Input in the following format:

H W

Output

Print the minimum possible value of S_{max} - S_{min}.

Sample Input 1

3 5

Sample Output 1

0

In the division below, S_{max} - S_{min} = 5 - 5 = 0.

Sample Input 2

4 5

Sample Output 2

2

In the division below, S_{max} - S_{min} = 8 - 6 = 2.

Sample Input 3

5 5

Sample Output 3

4

In the division below, S_{max} - S_{min} = 10 - 6 = 4.

Sample Input 4

100000 2

Sample Output 4

1

Sample Input 5

100000 100000

Sample Output 5

50000

Solution in Scala (2.11.7) (judge verdict: Accepted)

import java.{util => ju}
import scala.collection.{mutable => mu}
import MyPredef._


object Main extends App {
    val H,W = nextLong
    var h=Math.min(H,W)
    var w=Math.max(H,W)
    //val h=Math.max(H,W)
    //val w=Math.min(H,W)
    //val h=H
    //val w=W
    
    val res = if(h%3==0||w%3==0){
        0
    }else{
        var res = h
        
        (Math.max(w/3,0) to Math.min(w,w/3+1)).foreach(x => {
            val wx = w-x
            val h0 = h/2
            val h1 = h-h/2
            val can = Seq(x*h,wx*h0,wx*h1)
            res = Math.min(res,can.max-can.min)
        })
         
        (Math.max(h/3,0) to Math.min(h,h/3+1)).foreach(x => {
            val hx = h-x
            val w0 = w/2
            val w1 = w-w/2
            val can = Seq(x*h,hx*w0,hx*w1)
            res = Math.min(res,can.max-can.min)
        })
        
        h=Math.max(H,W)
        w=Math.min(H,W)
        
        (Math.max(w/3,0) to Math.min(w,w/3+1)).foreach(x => {
            val wx = w-x
            val h0 = h/2
            val h1 = h-h/2
            val can = Seq(x*h,wx*h0,wx*h1)
            res = Math.min(res,can.max-can.min)
        })
         
        /*
        (Math.max(h/3,0) to Math.min(h,h/3+1)).foreach(x => {
            val hx = h-x
            val w0 = w/2
            val w1 = w-w/2
            val can = Seq(x*h,hx*w0,hx*w1)
            res = Math.min(res,can.max-can.min)
        })
        */
        
        res
    }
    
    println(res)
}


object MyPredef {
  @inline def rep(n: Int, f: => Unit): Unit = { var c = 0; while (c < n) { f; c += 1 } }
  @inline def rep(n: Int, f: Int => Unit): Unit = { var c = 0; while (c < n) { f(c); c += 1 } }

  private val buf = new Array[Byte](1024); private var ptr = 0; private var len = 0
  @inline private def isPrintableChar(c: Int): Boolean = 33 <= c && c <= 126
  @inline private def hasNextByte(): Boolean =
    if (ptr >= len) { ptr = 0; len = System.in.read(buf); len > 0 } else { true }
  @inline private def hasNext(): Boolean = {
    while (hasNextByte() && !isPrintableChar(buf(ptr))) ptr += 1
    hasNextByte()
  }
  @inline private def readByte(): Byte =
    if (hasNextByte()) { val res = buf(ptr); ptr += 1; res } else { -1 }
  def next(): String = {
    if(!hasNext()) ???
    val sb = new StringBuilder; var b = readByte()
    while (isPrintableChar(b)) { sb.append(b.toChar); b = readByte() }
    sb.toString
  }
  def nextInt(): Int = {
    val n = nextLong()
    if (n < Int.MinValue || Int.MaxValue < n) ???
    n.toInt
  }
  def nextLong(): Long = {
    if(!hasNext()) ???
    var minus = false; var b = readByte()
    if (b == '-') { minus = true; b = readByte() }
    def go (b: Byte, n: Long = 0): Long =
      if ('0' <= b && b <= '9') { go(readByte(), n * 10 + b - '0') }
      else if (minus) { -n } else { n }
    go(b)
  }
  def nextDouble(): Double = next.toDouble
}
object MyArray {
  def fillT[T : scala.reflect.ClassTag](dimX: Int, dimY: Int)(f: => T): Array[Array[T]] = {
    val arrs = Array.ofDim[T](dimX, dimY)
    for {
      y <- (0 until dimY)
      x <- (0 until dimX)
    } {
      arrs(x)(y) = f
    }
    arrs
  }
}