import strscans

var (_, w, h, c) = stdin.readAll.scanTuple"$i $i $c"

for _ in 0..<h:
  var s = ""
  for _ in 0..<w:
    s.add c
    
    if c == 'W':
      c = 'B'
    else:
      c = 'W'
  
  echo s

  if s[0] == 'W':
    c = 'B'
  else:
    c = 'W'