using System;
class A {
public int x = 0;
public void f () { Console.WriteLine ( "A:f" ); } }
class B : A {
public int x = 1;
public void f () { Console.WriteLine ( "B:f" ); } }
public class Program {
public static void Main ( String [] args ) {
A a = new A ();
B b = new B ();
A ab = new B ();
a.f();
b.f();
ab.f();
Console.WriteLine ( a.x );
Console.WriteLine ( b.x );
Console.WriteLine ( ab.x ); } }
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