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 War on Terror, spanning decades, is a multi-trillion-dollar war. According to the Costs of War Project at Brown University's Watson Institute, the War on Terror will have cost $5.6 trillion for operations between 2001-2018 plus anticipated future costs of veterans' care. According to the Soufan Group in July 2015, the U.S. government was spending $9.4 million per day in operations against ISIS in Syria and Iraq. A March 2011 Congressional report estimated war spending through the fiscal year 2011 at $1.2 trillion, and future spending through 2021  at $1.8 trillion. A June 2011 academic report covering additional areas of war spending estimated it through 2011 at $2.7 trillion, and long-term spending at $5.4 trillion including interest. 
Question: How many years would spending at 1.2 trillion for operations at ISIS increase to 1.8 million? 
Answer type: Number 
Output:

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.
user
10.