using System;

​

namespace ClassLesson{  

    public class Person{

        public static int myAge;

        public static void SetAge (int n){

            myAge = n;

        }

        public static void SayHello (){

            Console.WriteLine("Hello");

        }

    }

    public class Student: Person{

        public static void ShowAge(){

            Console.WriteLine("My age is: {0} years old",Person.myAge);

        }

        public static void GoToClasses(){

            Console.WriteLine("I’m going to class.");

        }   

    }

    public class Teacher: Person{

        private string subject;

        public static void Explain(){

            Console.WriteLine("Explanation begins");

        }   

    }

public class StudentAndTeacherTest

{

    public static void Main()

    {

        Person.SayHello();

        Student.SetAge(40);

        Student.SayHello();

        Student.ShowAge();

        Teacher.SetAge(30);

        Teacher.SayHello();

        Teacher.Explain();

    }

}

}