The first line contains four space-separated integers r, c, v and h (1 ≤ v ≤ r ≤ 50, 1 ≤ h ≤ c ≤ 50) where the checkerboard is to have r rows and c columns, with v rectangles vertically and h rectangles horizontally.
Each of the next v lines contain a single positive integer a. The sum of the a values will be exactly r. These are the heights of the v rectangles in each column, in order from top to bottom.
Each of the next h lines contain a single positive integer b. The sum of the b values will be exactly c. These are the widths of the h rectangles in each row, in order from left to right.
Print the described checkerboard, in the form of r strings of length c, one per line. The strings should only contain the characters upper-case B (for a Black square) and upper-case W (for a White square).