import java.util.List;

class Ideone {
	
	static abstract class A {
		
		abstract List m1();
		
		abstract List<List> m2();
		
	}
	
	static class B extends A {
		
		List<?> m1() {
			return null;
		}
		
		List<List<?>> m2() {
			return null;
		}
		
	}
	
	public static void main(String[] args) {
		System.out.println("Yo.");
	}
	
}