import gen.*;
import edu.neu.ccs.demeterf.*;

class Magic extends Bc {
  // magically replace apples by oranges and vice versa
  // and keep the rest of the structure the same
      Orange combine(Apple a){return new Orange();}
      Apple  combine(Orange o){return new Apple();}
  public static Start magic(Start s){
    return new Traversal(new Magic()).<Start> traverse(s);
  }
}