"Good for your health" and "bad for your health" are generalizations. Each thing we do affects specific organs in specific ways. When we smoke, we accumulate tar in our lungs, reduce our oxygen capacity, and develop a nicotine addiction. When we exercise, we get various benefits, depending on the exercise. If you're going to smoke, better to get exercise, too. Moderate walking with deep breathing would be best. But, as others have noted, no exercise eliminates the damage done by smoking. If you are truly interested in health, best to stop the smoking.