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Further, the only way to find an input that hashes into an arbitrary set of outputs is again to try hashing different inputs one by one. So, if I challenged you to find an input whose (binary) hash value begins with 10 zeros, you would have to try numerous inputs, and you would find that each output had a 1/210 chance of beginning with 10 zeros, which means that you would have to try on the order of 210 inputs, or approximately 1,000 hash computations.