import strutils, sequtils

let
  t = stdin.readLine.split
  (W, H, C) = (t[0].parseInt, t[1].parseInt, t[2])

for i in 0 ..< H:
  for j in 0 ..< W:
    stdout.write(["B", "W"][(int(C == "W") + j mod 2 + i) mod 2])
  echo()