Scroll down to see how it works. If you'd rather solve the problem yourself, don't scroll. . . . . . How it works (this is a spoiler): ========================================= We begin with a variable called i. i starts at one and continues going up by 1 333 times. For each value of i, we add i * 3 to the sum variable. This gives us the total of all the multiples of 3 up to 1000. We do the same with 5, looping 199 times (in order to exclude 1000 itself), adding i * 5 to "sum" for each value of i. However, we also check, before adding i *5, that i * 5 hasn't already been added during the threes stage (multiples of both 3 AND 5 should still only be counted once). The result? A variable called "sum" with our needed answer.
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