import io._ def countNucleotides (dna: Stream[Char]): List[Int] = { var a, c, g, t = 0 for (base <- dna) { base match { case 'A' => a += 1 case 'C' => c += 1 case 'G' => g += 1 case 'T' => t += 1 case c => println("Unknown character: " + c) } } List(a, c, g, t) } val dna = Source.fromInputStream(System.in).toStream.takeWhile(_ != '\n') println(countNucleotides(dna).mkString(" "))