"So you see if the chance of pregnancy is constant per..uh..encounter, and given that the condom just broke, we're on a spectrum from the chance of a second round roughly doubling the odds but the overall chance is still small, or it doesn't make much difference anyway. Either way, the numbers say we should go again."

that's not too abstract, I can see how this formula applies to sex

I tried using if for this: https://adventofcode.com/2023/day/12 but computer said no

The Fibonacci sequence might have been more appropriate.

Not if they were using contraception.