[Isolated]

Hello,

I'm designing a system and have got myself stuck.

Basically, what I'm trying to figure out is this:

If I have a 15-digit string of numbers for example:

Код:

149655893228335

How do I multiply every other number by 2? To add to this, how would I then check the result, and if the result per number is a 2-digit number, add the digits together to make it a single digit number?

I've tried using loops, and other methods but all without any luck.

My mathematics skills aren't very good.

I hope this makes sense.

Thank you,

Isolated.