Detailed Instructions: This task involves creating questions from a given passage that involve some kind of complex reasoning (including numerical reasoning).
The generated questions must require looking at more than one part of the passage to answer. Try to use a variety of reasoning types in your questions (some of the sample reasoning types are illustrated in the 'positive examples' field) and also have a variety of answer types (spans, numbers, dates). A span is a continuous phrase taken directly from the passage or question. In such questions, the answer spans are recommended to be five words. Questions with answer type "number", are expected to start with "How many". For instance, "How long did an event last?" can be phrased as "How many years did an event last?". To increase diversity, try to create more questions for which the answer will be multiple spans. Please create questions that require AT LEAST 2 arithmetic operations as illustrated in the 'positive examples' field. You are encouraged to try DIFFERENT COMBINATIONS of operations and not just limit to the combinations shown in those examples. The more challenging questions you create, the better it is.
Q: Passage: The Japanese attempted to deny the Russians use of Port Arthur. During the night of 13-14 February, the Japanese attempted to block the entrance to Port Arthur by sinking several concrete-filled steamers in the deep water channel to the port, but they sank too deep to be effective. A similar attempt to block the harbour entrance during the night of 3-4 May also failed. In March, the charismatic Vice Admiral Makarov had taken command of the First Russian Pacific Squadron with the intention of breaking out of the Port Arthur blockade. On 12 April 1904, two Russian pre-dreadnought battleships, the flagship Petropavlovsk and the Pobeda, slipped out of port but struck Japanese mines off Port Arthur. The Petropavlovsk sank almost immediately, while the Pobeda had to be towed back to port for extensive repairs. Admiral Makarov, the single most effective Russian naval strategist of the war, perished on the battleship Petropavlovsk. On 15 April 1904, the Russian government made overtures threatening to seize the British war correspondents who were taking the ship Haimun into warzones to report for the London-based Times newspaper, citing concerns about the possibility of the British giving away Russian positions to the Japanese fleet. The Russians quickly learned, and soon employed, the Japanese tactic of offensive minelaying. On 15 May 1904, two Japanese battleships, the Yashima and the Hatsuse, were lured into a recently laid Russian minefield off Port Arthur, each striking at least two mines. The Hatsuse sank within minutes, taking 450 sailors with her, while the Yashima sank while under tow towards Korea for repairs. On 23 June 1904, a breakout attempt by the Russian squadron, now under the command of Admiral Wilgelm Vitgeft, failed. By the end of the month, Japanese artillery were firing shells into the harbour.
A:
How many days passed between the two Russian pre-dreadnaught battleships struck mines and the two Japanese battleships triking mines?