1. Problem: make generator of probability 1/3 using the normal coin (1/2).

Solution
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Two consecutive coin flips give us 4 combinations (head-head, tail-tail,
head-tail, tail-head). We can exclude one of these combinations
(just start everything from the beginning in the case of an
unwanted combination). We get three equally probable outcomes.

Add the first coin problem
Add the first coin problem

1/2 ---> 1/3
