Mirko doesn't like Latin homeworks so he made a bet with Slavko. Loser will be writing homeworks for both of them the entire month. Mirko wants to win so he designed this problem they could have something to bet on.

At his desk he found a cube, with numbers \(1\) to \(6\) on its faces. Additionally, sum of the numbers on opposing faces is equal to \(7\). That means that \(6\) is on the opposite face of \(1\), \(5\) on the opposite of \(2\) and \(4\) on the opposite face of \(3\).

Mirko has put the cube in the upper left field of the matrix of \(R\) rows and \(C\) columns. The cube is initially oriented in a way that upper side is showing number \(1\), and side to the right number \(3\).

Mirko now makes the following moves:

1. He is rolling the cube to the right, until it reaches the last column
2. Then he rolls it down (to the next row)
3. Now he rolls the cube to the left, until it reaches first column
4. Like in step 2, he rolls it down (to the next row)

Mirko is repeating these steps for as long as he can, i.e. as long as he can roll the cube in the next row. When a cube reaches some field, Mirko writes down the number on the top of the cube. In the end he sums all of the numbers he had written.

Mirko made a bet with Slavko that he could calculate that sum without error. Help Slavko verifying Mirko's solution!

In test cases worth 50% of total points, R and C will be less than or equal to 100.

First and only line of input contains two positive integers \(R\) and \(C\) (\(1 \le R, C \le 100\,000\)), matrix dimensions.

First and only line of output should contain the sum described in the task.

Scoring: In test cases worth \(50\%\) of total points, \(R\) and \(C\) will be less than or equal to \(100\).

riseoj 작성

출처 COCI 2011/2012 Contest 3