using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Interface
{
    class MyClass : IComparable
    {
        private int key;
        private int value;

        public int CompareTo(object obj)
        {
            MyClass target = obj as MyClass;
            if (target == null)
                throw new InvalidCastException();

            return this.key.CompareTo(target.key);
        }
    }
}