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What! I really want to know how you did this in 2-3 minutes... It took me about 15 minutes of intensive counting -.-

We'll see if I got it right, but counted 5-6 small cases, found a pattern, and guessed lol.

yeah, I figured the pattern between A and B too, but between B and C I didn't. It was hellish counting.

ye sometimes starting with small cases, discover the general formula, and apply it to large cases. can be one of the method to solve a math problem! :)

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