unexpected behavior of Object

 static void Main(string[] args)
        {

            object a = new  object();
            object cst=a;
            a = 6;
            Console.WriteLine(a + " " + cst);
                a="klm";
            Console.WriteLine(a+" "+cst);
}

output:

6  System.Object

klm System.Object

I expected the result as:

6  6 

klm  klm

Any explanation?