Hi i have to complete a program which do the following

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.

what this means ?

how to do it

i dont want yooou to do it but just give me hints

thanks