How to use biased coins to make unbiased decisions?

Two throws, if the two throws are the same, remove them, and take the front of different faces of the two throws as the income face. For example, if I bet heads to win, then if the results of the first two shots are positive, not counting, I will continue to vote twice until, for example, I throw tails, so the tails are regarded as victory according to the regulations, so I lost = = # because, assuming that the probability assumption of tails is X, then heads are 60.

Hope to adopt