fun readInt () =
    valOf (TextIO.scanStream (Int.scan StringCvt.DEC) TextIO.stdIn)

fun readChar () = valOf (TextIO.scanStream Char.scan TextIO.stdIn)



val () =
    let
        val w = readInt ()
        val h = readInt ()
        val c = readChar ()
                        
        fun printAns () =
            let
                fun makeLine 0 _ = []
                  | makeLine n ch = 
                    if ch = #"B" then #"W" :: makeLine (n - 1) #"W"
                    else #"B" :: makeLine (n - 1) #"B"
           
                fun makeLines 0 _ = ignore ()
                  | makeLines n ch =
                    if ch = #"B"
                    then
                        (
                          print (String.implode (List.rev (makeLine w #"W")) ^ "\n");
                          makeLines (n - 1) #"W"
                        )
                    else
                        (
                          print (String.implode (List.rev (makeLine w #"B")) ^ "\n");
                          makeLines (n - 1) #"B"
                        )          
            in    
                makeLines h c
            end
    in
        printAns ()
    end