Murzik made one of flowerbeds as a chess-board with the sizes M to N. Some flower grows in every cell of flowerbeds. Sometimes he took out Anfisa for a walk on this flowerbed (yes, not surprised, they are really friends). Anfisa moves on a flowerbed such as: she beginning always from an overhead left corner to right inferior corner. She picks flowers thus each time to pass on a new route, and Murzyk give her the piece of cheese on the exit.

   You have to count up what most quantity of the pieces of cheese will have Anfisa, if she all the time will try to save most of flowers.

   Input

   There is 2 numbers M and N in the unique line. Absence is between them.

   0 < M,N ≤ 2000000000.  

   Output

   There is one number. It is a most quantity of the pieces of cheese, which Anfisa can get.