public class C1 extends C2{
  public static void main(String[] args){
    new C1();
  }
  public C1(){
    System.out.println("c1's default constructor is invoked");
  }
}
class C2 extends C3{
  public C2(){
    System.out.println("c2's default constructor is invoked");
  }
}
class C3{
  public C3(){
    System.out.println("c3's default constructor is invoked");
  }
}