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 Ruby (2.3.3) (judge verdict: Accepted)

def culculate(a,b)
  ans=Float::INFINITY
  (1..a-1).each do |i|
    s1=i*b
    s2=(a-i)*(b/2)
    s3=(a-i)*(b-b/2)
    s22=((a-i)/2)*b
    s32=((a-i)-(a-i)/2)*b
    sort1=[s1,s2,s3].sort
    sort2=[s1,s22,s32].sort
    ans=[sort1[2]-sort1[0],sort2[2]-sort2[0],ans].min
  end
  return ans
end

h,w=gets.split.map(&:to_i)
if h%3==0 || w%3==0
  puts 0
  exit
end
puts [culculate(h,w),culculate(w,h)].min