class Program

     {

         static void Main(string[] args)

         {

             Console.WriteLine("-------------------------------------");

             IIntroduce iSE = new SoftwareEngineer();

             iSE.SayHi();

             iSE.DescribeMyself();

             iSE.SayGoodbye();

             Console.WriteLine("-------------------------------------");

             IIntroduce iTc = new Teacher();

             iTc.SayHi();

             iTc.DescribeMyself();

             iTc.SayGoodbye();

             Console.ReadKey();

         }

     }

     interface IIntroduce

     {

         void SayHi();

         void DescribeMyself();

         void SayGoodbye();

     }

    class SoftwareEngineer : IIntroduce

     {

         public void DescribeMyself()

         {

             Console.WriteLine("I'm a software engineer !");

         }

         public void SayGoodbye()

         {

             Console.WriteLine("Goodbye !");

         }

         public void SayHi()

         {

             Console.WriteLine("Hi !");

         }

     }

    class Teacher : IIntroduce

     {

         public void DescribeMyself()

         {

             Console.WriteLine("I'm a Teacher !");

         }

         public void SayGoodbye()

         {

             Console.WriteLine("Goodbye !");

         }

         public void SayHi()

         {

             Console.WriteLine("Hi !");

         }

     }