import java.io.*;

public class test_2 {
  static int x = 100;
  public static void main(String [] args){
    A a = new A();
    A b = new B();
    A c = new C();
    a.who();
    b.who();
    a.print_s();
    b.print_s();
    c.print_s();
  }
}

class A {
  public String s = "A";
  String name;
  public A() { name = "A"; }
  public A(String name) { this.name = name; }
  public void who(){ System.out.println("who="+name); }
  public void print_s() { System.out.println("s="+s); }
}

class B extends A {
  String s = "B";
  public B() { name = "B"; }
  public void print_s() { System.out.println("s="+s); }
}

class C extends B {
  public void print_s() { System.out.println("s="+s); }
}