import java.util.Vector;

class WCTest{
  
  void test()
  {
    Vector<Vector<? extends Sub1>> v1 = new Vector<Vector<Sub2>>();
  }

}

class Sub1 {}

class Sub2 extends Sub1 {}

class Sub3 extends Sub2 {}

class N<x> {}

class Test<x> extends N<N<? extends x>> {}