A stack of cubes covers part of a grid 3 squares wide and 2 deep. Its front and side views are drawn. What is the least number of cubes it can have?

Bottom layer: the front view needs all 3 lines and the side view both rows, so at least 3 cubes. Second layer: 2 lines but only 1 row (the front row in the side view is 2 high), so 2 cubes in that row. Least $3+2=5$. (8 is the greatest possible.)