using System;
using System.Collections.Generic;
using System.Text;

namespace InterfaceExample
{
    class Program
    {
        static void Main(string[] args)
        {
            IClass Bar;
            string input = Console.ReadLine();
           
            switch (input)
            {
                case "Class1":
                    Bar = new Class1();
                    break;

                case "Class2":
                    Bar = new Class2();
                    break;

                default:
                    return;
            }

            Bar.Foo();
            Console.ReadLine();
        }

    }

    interface IClass
    {
        string Foo();
    }

    class Class1 : IClass
    {
        public string Foo()
        {
            Console.WriteLine("1");
            return "1";
        }
    }

    class Class2 : IClass
    {
        public string Foo()
        {
            Console.WriteLine("2");
            return "2";
        }
    }
}