Input: Article: Of the five original great powers recognised at the Congress of Vienna, only France and the United Kingdom have maintained that status continuously to the present day, although France was defeated in the Franco-Prussian War and occupied during World War II. After the Congress of Vienna, the British Empire emerged as the pre-eminent power, due to its navy and the extent of its territories, which signalled the beginning of the Pax Britannica and of the Great Game between the UK and Russia. The balance of power between the Great Powers became a major influence in European politics, prompting Otto von Bismarck to say "All politics reduces itself to this formula: try to be one of three, as long as the world is governed by the unstable equilibrium of five great powers."

Now answer this question: Who stated that "All politics reduces itself to this formula: try to be one of three, as long as the world is governed by the unstable equilibrium of five great powers.?"

Output: Otto von Bismarck

Input: Article: Zhejiang's main manufacturing sectors are electromechanical industries, textiles, chemical industries, food, and construction materials. In recent years Zhejiang has followed its own development model, dubbed the "Zhejiang model", which is based on prioritizing and encouraging entrepreneurship, an emphasis on small businesses responsive to the whims of the market, large public investments into infrastructure, and the production of low-cost goods in bulk for both domestic consumption and export. As a result, Zhejiang has made itself one of the richest provinces, and the "Zhejiang spirit" has become something of a legend within China. However, some economists now worry that this model is not sustainable, in that it is inefficient and places unreasonable demands on raw materials and public utilities, and also a dead end, in that the myriad small businesses in Zhejiang producing cheap goods in bulk are unable to move to more sophisticated or technologically more advanced industries. The economic heart of Zhejiang is moving from North Zhejiang, centered on Hangzhou, southeastward to the region centered on Wenzhou and Taizhou. The per capita disposable income of urbanites in Zhejiang reached 24,611 yuan (US$3,603) in 2009, an annual real growth of 8.3%. The per capita pure income of rural residents stood at 10,007 yuan (US$1,465), a real growth of 8.1% year-on-year. Zhejiang's nominal GDP for 2011 was 3.20 trillion yuan (US$506 billion) with a per capita GDP of 44,335 yuan (US$6,490). In 2009, Zhejiang's primary, secondary, and tertiary industries were worth 116.2 billion yuan (US$17 billion), 1.1843 trillion yuan (US$173.4 billion), and 982.7 billion yuan (US$143.9 billion) respectively.

Now answer this question: What direction is the economic heart of Zhejiang moving toward?

Output: southeast

Input: Article: The service's B-2A aircraft entered service in the 1990s, its B-1B aircraft in the 1980s and its current B-52H aircraft in the early 1960s. The B-52 Stratofortress airframe design is over 60 years old and the B-52H aircraft currently in the active inventory were all built between 1960 and 1962. The B-52H is scheduled to remain in service for another 30 years, which would keep the airframe in service for nearly 90 years, an unprecedented length of service for any aircraft. The B-21 is projected to replace the B-52 and parts of the B-1B force by the mid-2020s.

Now answer this question: When did the B-2A aircraft enter into service of the US Air Force?

Output:
1990s