object Main extends App {
	def countSimilar(str: String, ch: List[Char]): String = {
	  def process(l: List[Char], acc: String = ""): String = {
	    l match {
	      case Nil => acc
	      case h :: _ =>
	        val tw = l.takeWhile(_ == h)
	        acc + process(
	          l.drop(tw.length),
	          if (ch.contains(h)) h + tw.length.toString else tw.mkString("")
	        )
	    }
	  }
 
	  process(str.toList)
	}
 
	println(countSimilar("aaaabbbcccss", List('a', 'b')))
	println(countSimilar("aaaabbbcccssaaaabb", List('a', 'b', 'c')))
}

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