// Original program. No problems.

using System;

class A {

  public void M1(){
    Console.WriteLine("Method 1");
  }
}

class B: A {
  
  public void M2(){
    Console.WriteLine("Dangerous Method 2");
  }
}

class Client{
  
  public static void Main(){
    A a = new B();
    B b = new B();

    a.M1();  // Nothing dangerous expected
//  a.M2();  // Compile-time error
             // 'A' does not contain a definition for 'M2'
    b.M2();  // Expects dangerous operation
  }
}