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


fun readStr () =
    let
        fun scan reader stream = SOME (StringCvt.splitl (not o Char.isSpace) reader (StringCvt.skipWS reader stream))
    in
        valOf (TextIO.scanStream scan TextIO.stdIn)
    end


exception E
fun countWhite nil = 0
  | countWhite (#"R" :: tl) = countWhite tl
  | countWhite (#"W" :: tl) = 1 + countWhite tl
  | countWhite _ = raise E


fun findAns nil = 0
  | findAns (h :: tl) =
    countWhite (String.explode h) + findAns tl


val () =
    let
        val n = readInt ()
        val m = readInt ()
        val a_s = List.tabulate (n, fn _ => readStr ())

        val ans = findAns a_s
    in
        print (Int.toString ans ^ "\n")  
    end