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 C (GCC 5.4.1) (judge verdict: Wrong Answer)

#include<stdio.h>
int main(void)
{
	long long a,b,t;
	scanf("%lld%lld",&a,&b);
	if(a<b)
	{
		t=a;
		a=b;
		b=t;
	}
	if(a%3==0||b%3==0)
	printf("0\n");
	else
	{
		if(a%2==1&&b%2==1)
		{
			t=(b/2*a)-(b/2+1)*(a/2);
			printf("%lld\n",t);
		}
		else if(a%2==0&&b%2==0)
		{
			b=b/2;
			printf("%lld\n",b);	
		}
		else if(a%2==0&&b%2==1)
		{
			a=a/2;
			printf("%lld\n",a);
		}
		else if(a%2==1&&b%2==0)
		{
			b=b/2;
			printf("%lld\n",b);
		}
	}
	return 0;
}