You are given a rectangular board of *M* × *N* squares. Also you are given an unlimited number of standard domino pieces of 2 × 1 squares. You are allowed to rotate the pieces. You are asked to place as many dominoes as possible on the board so as to meet the following conditions:

1. Each domino completely covers two squares.

2. No two dominoes overlap.

3. Each domino lies entirely inside the board. It is allowed to touch the edges of the board.

Find the maximum number of dominoes, which can be placed under these restrictions.
In a single line you are given two integers *M* and *N* — board sizes in squares (1 ≤ *M* ≤ *N* ≤ 16).
dim=input("")              #se crea un input para ingresar las dimnesiones  
dim_lista=dim.split(" ")   #este comando separa los elementos ingresado al input 
dim_entero=[int(i)for i in dim_lista]   #transfromar en entero los elementos el int y se agregan a una lista 
espacio=dim_entero[0]*dim_entero[1]     #el espacio disponible va a ser el area del rectangulo
domino=2                               #una piez de domino ocuoa dos espacios 
if espacio%domino==0:
  print(int(espacio/domino))           #si el modulo del espacion entre 2(domino) es 0,caben (espacio/domino) piezas
elif espacio%domino!=0:
  print(int((espacio-1)/2))             #si el modulo del espacion entre 2(domino) es !=0,caben (espacio-1/2) piezas