toStrList x = map return x::[String]
fil x = filter (\t -> t == "C" || t == "F") x
check :: String -> String
check str = if(take 2 str  == "CF")then  "Yes" else if length(str) == 1 then "No" else  check (drop 1 str)
main = do
        n <- getLine
        putStrLn ((check.concat.fil.toStrList) n)