Suppose you are given a Turing machine M (not necessarily a decider), a string w, and a magic genie. You can ask the magic genie whether a certain Turing machine halts on a certain input string, and the genie will magically give you the correct yes/no answer. You can ask the genie as many such questions as you like, about any Turing machine and any string. Describe a strategy you can use to decide whether M accepts w. Remember to decide means to say with certainty that M accepts w or that M does not accept w.

Any ideas would be much appreciated.