Sarah is on a diet and tracks her daily calorie intake. She consumes 1500 calories each day. In the first week, she follows this diet strictly for 7 days. In the second week, she increases her daily intake by 200 calories and follows this for another 7 days. In the third week, she reduces her intake by 100 calories from her original daily intake and follows this for 7 days. How many calories does Sarah consume in total over the three weeks? Let's think step by step and output the final answer within \boxed{}.
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