MEMO 2016 T3

A $8 \times 8$ board is given, with sides directed north-south and east-west. It is divided into $1 \times 1$ cells in the usual manner. In each cell, there is most one house. A house occupies only one cell.

A house is in the shade if there is a house in each of the cells in the south, east and west sides of its cell. In particular, no house placed on the south, east or west side of the board is in the shade.

Find the maximal number of houses that can be placed on the board such that no house is in the shade.