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).
def max_dominoes(m, n):
  """
  Finds the maximum number of dominoes that can be placed on a rectangular board of size m * n.

  Args:
    m: The number of rows in the board.
    n: The number of columns in the board.

  Returns:
    The maximum number of dominoes that can be placed on the board.
  """

  if m == 0 or n == 0:
    return 0

  if m == 1 or n == 1:
    return min(m, n)

  # First, we can place dominoes in a grid pattern, with each domino covering two squares.
  # This will fill the board up to the last row and column, leaving a single square uncovered.

  grid_dominoes = m * n // 2

  # If the last row or column is odd, we can place one more domino in that row or column.

  if m % 2 == 1:
    grid_dominoes += 1
  elif n % 2 == 1:
    grid_dominoes += 1

  return grid_dominoes


if __name__ == "__main__":
  m, n = map(int, input().split())

  print(max_dominoes(m, n))
