def sumOfNodes(node:BT[Int]):Int = {
    def sumOfNodes_superHiperFunction(node:BT[Int],accum:Int):Int=
    node match {
      case Empty() => accum
      case Node(v, l, r) => sumOfNodes_superHiperFunction(l,sumOfNodes_superHiperFunction(r,v+accum))
    }
    sumOfNodes_superHiperFunction(node,0)
  }