Illinois Senator Mark Kirk is doing very well after suffering a stroke in January.  Doctors at the Rehabilitation Institute of Chicago say he's mentally sharp, walking up stairs and even exercising.  Institute Director Richard Harvey says the Senator is fully engaged in all aspects of his rehabilitation program.  While Kirk is showing excellent signs of improvement, he's still not functioning at the same level he was before he had the stroke.  Doctors are working with him to improve his walk speeds and they're confident he will make a full recovery.