object Main extends App {
  val sc = new java.util.Scanner(System.in)
  val n,s,t = sc.next
  
  val composed = (s.zipWithIndex.map{case (e, index) => (e, index * 2)} ++ t.zipWithIndex.map{case (e, index) => (e, index * 2 + 1)}).sortBy(_._2)  
  
  println(composed.map{case (e, _) => e}.mkString)
}