At the end of 1695 the Russians began preparing for the second Azov campaign. By the spring of 1696 they had built a fleet of ships to block Turkish reinforcements for the garrison. The cavalry under the command of Sheremetev  was once again sent to the lower reaches of the Dnieper. From April 23-26 the main forces  under the command of Aleksei Shein started to advance towards Azov by land and water . Peter I and his galley fleet left for Azov on May 3. On May 27 the Russian fleet  under the command of Lefort reached the sea and blocked Azov. On June 14 the Turkish fleet  appeared at the mouth of the Don. However, it left after having lost two ships in combat. After massive bombardment from land and sea and seizure of the external rampart of the fortress by the Ukrainian and Don Cossacks on July 17, the Azov garrison surrendered on July 19.
Question: How many days passed between the Russian fleet blocking Azov and the Turkish fleet appearing at the mouth of the Don?
Answer: 18