Первые дни после объявления войны ознаменовались массовыми патриотическими манифестациями во многих городах Российской империи.

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Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
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The first few days after the declaration of war were marked by massive patriotic demonstrations in many cities of Russia empire.