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 solve(m, n):
  """
  Solves the domino problem.

  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.
  """

  # Initialize the maximum number of dominoes to 0.
  max_dominoes = 0

  # Iterate over all possible ways to place dominoes on the board.
  for i in range(m):
    for j in range(n):
      # Check if the current position is valid.
      if i + 1 < m and j + 1 < n:
        # Place a domino at the current position.
        max_dominoes += 1

  return max_dominoes


if __name__ == "__main__":
  # Get the input from the user.
  m, n = map(int, input().split())

  # Solve the problem.
  max_dominoes = solve(m, n)

  # Print the output.
  print(max_dominoes)
