In this task you will be given an answer to a question. You need to generate a question. The answer given should be a correct answer for the generated question.

Example Input: The Old Kingdom, in ancient Egyptian history, is the period in the third millennium (c. 2686 -- 2181 BC) also known as the' Age of the Pyramids' or' Age of the Pyramid Builders' as it includes the great 4th Dynasty when King Sneferu perfected the art of pyramid building and the pyramids of Giza were constructed under the kings Khufu, Khafre and Menkaure. Egypt attained its first continuous peak of civilization -- the first of three so-called 'Kingdom' periods (followed by the Middle Kingdom and New Kingdom) which mark the high points of civilization in the lower Nile Valley.
Example Output: how long did the old kingdom period of egyptian civilization last

Example Input: In mid-1961, President Ngo Dinh Diem of South Vietnam asked the United States to conduct aerial herbicide spraying in his country. In August of that year, the Republic of Vietnam Air Force conducted herbicide operations with American help. But Diem's request launched a policy debate in the White House and the State and Defense Departments. However, U.S. officials considered using it, pointing out that the British had already used herbicides and defoliants during the Malayan Emergency in the 1950s. In November 1961, President John F. Kennedy authorized the start of Operation Ranch Hand, the codename for the U.S. Air Force's herbicide program in Vietnam.
Example Output: when did the us start using agent orange in vietnam

Example Input: The Preamble to the United States Constitution is a brief introductory statement of the Constitution's fundamental purposes and guiding principles. It states in general terms, and courts have referred to it as reliable evidence of the Founding Fathers' intentions regarding the Constitution's meaning and what they hoped the Constitution would achieve.
Example Output:
main idea of the preamble to the constitution