"Math and computer science—although not as common as it should be, if you listen to some of the computer scientist mathematicians I've known. Math and physics. In general, any two fields that are either closely related or directly useful to each other. If I could go back and do my education in a sensible order, I'd do math and physics instead of physics and biochemistry as my undergraduate majors. But then, if I'd done that in the first place, I wouldn't be here trying to find out if I really want the rest of that medical degree, because I would never have started it."