Because multiple convictions may not be based on necessarily included offenses, a defendant cannot be convicted of both robbery and petty theft with a prior conviction when the crimes arose from the same incident. Appellant took a car navigation system from a store display and left the store without paying for it. When followed by a store employee, appellant turned and pointed a silver object at the employee. Thinking that the object was a gun, the employee gave up the chase. Appellant was convicted of robbery and petty theft with a prior conviction (Pen. Code, sec. 666). The conviction for petty theft with a prior conviction was reversed as the offense was a lesser included offense within the robbery. The prior conviction aspect of section 666 was a sentencing factor, rather than an element of the crime of theft, and, thus, did not distinguish it as a separate theft crime from robbery.