class A {
public void showName() {
System.out.println("A");
}
}
class B extends A {
public void showName() {
System.out.println("B");
}
}
class C extends B {
public void showName() {
System.out.println("C");
}
}
class D extends C {
public void showName() {
System.out.println("D");
}
}