Resolve Gem Stones in functional programming way

hackerrank Gem Stones.scala

object Solution { 
  def intersect(a: Set[Char], b: Set[Char]) = a & b
  def main(args: Array[String]) {
    val lines =io.Source.stdin.getLines().toList
    val cases = lines.drop(1)
    val caseSets = cases.map(c => c.distinct).map(c => c.toSet)
    val resultSet = caseSets.reduce(intersect)
    println(resultSet.size)
  }
}