Given the stream of consciousness rationale, provide a reasonable question and answer. Rationale: First find the number of marshmallows Jacob needs: 48 graham crackers / 2 graham crackers / marshmallow = 24 marshmallows. Then subtract the number of marshmallows Jacob already has from the number he needs to find the number he needs to buy: 24 marshmallows - 6 marshmallows = 18 marshmallows.
 The question and answer:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
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Jacob is making s'mores. Each s'more takes two graham crackers and one marshmallow. If Jacob has 48 graham crackers and 6 marshmallows, how many more marshmallows does he need to buy?
The answer is 18