Loops. [H] If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23. Find the sum of all the multiples of 3 or 5 below 1000. Hint: Be careful not to add two times a number which is multiple of both 3 and 5.

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