object Main extends App {
val s = scala.io.StdIn.readLine.split("")

val result = if (s.length == 1) {
  s(0)
} else if (s.length % 2==0){
  s.grouped(2).toList.transpose.head.foldLeft("")(_+_)
} else {
  (s.head +: s.tail.grouped(2).toList.transpose.tail.head).foldLeft("")(_+_)
}
println(result)
}