object Main {
  def main(args: Array[String]): Unit = {
    import scala.io.StdIn.readLine
    val Array(datN) = readLine.split(" ").map(_.toInt)
    val datA = for(i <- 1 to 2) yield (readLine.split(" ").map(_.toInt))

    val ans = (0 until datN).map(x => datA(0).take(x + 1).sum + datA(1).takeRight(datN - x).sum).max
    println(ans)
  }
}
