Definition: This task involves creating answers to complex questions, from a given passage. Answering these questions, typically involve understanding multiple sentences. Make sure that your answer has the same type as the "answer type" mentioned in input. The provided "answer type" can be of any of the following types: "span", "date", "number". A "span" answer is a continuous phrase taken directly from the passage or question. You can directly copy-paste the text from the passage or the question for span type answers. If you find multiple spans, please add them all as a comma separated list. Please restrict each span to five words. A "number" type answer can include a digit specifying an actual value. For "date" type answers, use DD MM YYYY format e.g. 11 Jan 1992. If full date is not available in the passage you can write partial date such as 1992 or Jan 1992. If you find multiple spans, please add them all as a comma separated list. Please restrict each span to five words.
Input: Passage: The Tepehuan suffered a series of devastating epidemics of European-introduced diseases in the years before the revolt. Epidemics were known to have occurred in their region in 1594, 1601-1602, 1606-1607, 1610, and 1616-1617. The Tepehuan and their neighbors may have been reduced in population by more than 80 percent by the epidemics, from a pre-Columbian population of more than 100,000 to fewer than 20,000, of which the Tepehuan may have been one-half of this total During the Chichimeca war the Tepehuan remained neutral although urged by the Chichimecas to join them in resistance to Spanish expansion. The Spanish failed to defeat the Chichimeca militarily and instituted a new policy called "peace by purchase" in which Catholic missionaries would be a major tool in pacifying hostile and semi-hostile Indians. Indians were to be supplied with food and tools and resettled into towns. Missionaries, rather than the military, would take on most of the responsibility for integrating the Indians into Mexican and Christian society. The Acaxee and Xixime were the first to have this new Spanish policy applied to them and the Tepehuan would be next.
Question: How many years was there in between the first year where epidemics were known to have occurred and the last year?
Answer type: Number
Output:
23.