POGODAK#9430

POGODAK

1 second
32 megabytes
Very easy

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

At his desk he found a cube, with numbers to on its faces. Cube is shown on the picture. Additionally, sum of the numbers on opposing faces is equal to . That means that is on the opposite face of , on the opposite of and on the opposite face of .

Huseyn has put the cube in the upper left field of the matrix of rows and columns. The cube is initially oriented in a way that upper side is showing number , and side to the right number .

Screenshot from 2019-11-07 19-35-29.png

Huseyn 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)

Huseyn 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, Huseyn writes down the number on the top of the cube. In the end he sums all of the numbers he had written.

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

Input

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

Output

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

Examples

Example 1

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Example 2

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Example 3

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Note

Screenshot from 2019-11-07 19-47-35.png

Numbers Huseyn wrote down are: