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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.

function calculate_multiples {

    $SUM = 0

    1..999 | ForEach-Object {
        if (!( $_ % 3) -OR !($_ % 5)) {
            $Sum += $_
        }
    }

  return $Sum
}