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)

h,w = map(int,input().split())
if h%3 == 0 or w%3 == 0:
    print(0)
    exit()

ans = float('inf')
for i in range(1,w):
    s = []
    s.append(i*h)
    if h%2 == 1:
        s.append((w-i)*(h//2+1))
    s.append((w-i)*(h//2))
    ans = min(ans,max(s)-min(s))

for i in range(1,h):
    s = []
    s.append(i*w)
    if w%2 == 1:
        s.append((h-i)*(w//2+1))
    s.append((h-i)*(w//2))
    ans = min(ans,max(s)-min(s))

ans = min(ans, h*(w//2+1) - h*(w//2), w*(h//2+1) - w*(h//2))
print(ans)