import scala.io.StdIn

object Main extends App {

  val s = StdIn.readLine()

  def conv(t: StringBuilder, i: Int): StringBuilder = {
    if (s.length < i) {
      t
    }else if (i % 2 == 1) {
      t.append(s(i - 1))
      conv(t, i + 1)
    } else {
      conv(t, i + 1)
    }
  }

  println(conv(new StringBuilder, 1))

}