Maximizing Trees in a Garden

You are given a garden with m rows and n columns. You need to plant as many trees as possible under the following conditions:

• No two trees are planted in the same row or column.
• The Manhattan distance between any two trees is at least 2. That is, for any two trees at positions \((i_1, j_1)\) and \((i_2, j_2)\), the condition
  \(|i_1 - i_2| + |j_1 - j_2| \ge 2\) must hold.

It can be shown that the maximum number of trees that can be planted is given by the formula:

$$\left\lfloor \frac{m+1}{2} \right\rfloor \times \left\lfloor \frac{n+1}{2} \right\rfloor$$

Your task is to compute this value given m and n.

inputFormat

The input consists of two space-separated integers m and n on a single line.

outputFormat

Output a single integer representing the maximum number of trees that can be planted in the garden.

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4