The task of "6B"
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Ben, Billy, Bob and Blake have gems.
Ben - has a round, blue, sapphire;
oval, blue, sapphire;
round, white, diamond;
oval, white, diamond.
They placed the ads about selling of the gems in the Internet.
Ben: A beautiful blue sapphire is for sale;
Billy: An e
sapphire is for sale;
Bob: An e
diamond is for sale;
Blake: A b
hite diamond is for sale.
Bonnie wants to buy round gems.
How can she get only Ben's and Bob's ads in Internet?
They don't know each other.
Only Sergey Brin knows the exact solution.