The owner of a local jewellery store hired 3 watchmen to guard his diamonds, but a thief still got in and stole some diamonds. On the way out, the thief met each watchman, one at a time. To each he gave ½ of the diamonds he had then, and 2 more besides. He escaped with one diamond. How many did he steal originally?

• A. 40
• B. 36
• C. 25
• D. None of these