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 Python (3.4.3) (judge verdict: Accepted)

from math import ceil, floor
def chocolateBar():
    h,w=map(int,input().split())
    ans=10**18

    #縦に三等分する場合
    ans=min(ans, (ceil(w/3)-floor(w/3))*h )
    ans=min(ans, (ceil(h/3)-floor(h/3))*w )

    #縦横に一回ずつ
    for i in range(1, h):
        s1=i*w
        s2=(h-i)*floor(w*0.5)
        s3=(h-i)*ceil(w*0.5)
        ans=min(ans, max(s1,s2,s3)-min(s1,s2,s3))
    for i in range(1, w):
        s1=i*h
        s2=(w-i)*floor(h*0.5)
        s3=(w-i)*ceil(h*0.5)
        ans=min(ans, max(s1,s2,s3)-min(s1,s2,s3))
    
    return ans

print(chocolateBar())