module SumOfMultiples

let isMultiple factors number = 
    List.fold (fun a x -> (a || number % x = 0)) false factors

let sum (factors: int list) (upperBound: int): int = 
    let goodFactors = List.filter (fun i -> i <> 0) factors
    let numbers = [ for i in 1..(upperBound - 1) -> i]
    List.sum (List.filter (fun el -> isMultiple goodFactors el) numbers)