Fair coin probability of Heads

I have a fair coin which I toss many times. What is the probability that it takes 12 rolls until I get two heads in a row?

I thought this was just standard geometric. But it doesn’t seem to work? Can someone please explain how to do this?

I have a fair coin which I toss many times. What is the probability that it takes 12 rolls until I get two heads in a row?

I thought this was just standard geometric. But it doesn’t seem to work? Can someone please explain how to do this?