The table surface is divided into N by M square cells. Some cubes are stacked one upon another over the cells, forming towers. For each cell the number of cubes stacked over it is given in the matrix A. -The table surface is divided into N by M squa 're cells. Some cubes are stacked one upon anothe r over the cells. forming towers. For each cell the number of cube 's stacked over it is given in the matrix A.