This task is about writing a correct answer for the reading comprehension task. Based on the information provided in a given passage, you should identify the shortest continuous text span from the passage that serves as an answer to the given question. Avoid answers that are incorrect or provides incomplete justification for the question.

Input: Consider Input: Passage: The Yuan dynasty is considered both a successor to the Mongol Empire and an imperial Chinese dynasty. It was the khanate ruled by the successors of Möngke Khan after the division of the Mongol Empire. In official Chinese histories, the Yuan dynasty bore the Mandate of Heaven, following the Song dynasty and preceding the Ming dynasty. The dynasty was established by Kublai Khan, yet he placed his grandfather Genghis Khan on the imperial records as the official founder of the dynasty as Taizu.[b] In the Proclamation of the Dynastic Name (《建國號詔》), Kublai announced the name of the new dynasty as Great Yuan and claimed the succession of former Chinese dynasties from the Three Sovereigns and Five Emperors to the Tang dynasty. Question: Who was Kublai Khan's grandfather?

Output: Genghis Khan


Input: Consider Input: Passage: Cultural and career issues in the U.S. Air Force have been cited as one of the reasons for the shortfall in needed UAV operators. In spite of an urgent need for UAVs or drones to provide round the clock coverage for American troops during the Iraq War, the USAF did not establish a new career field for piloting them until the last year of that war and in 2014 changed its RPA training syllabus again, in the face of large aircraft losses in training, and in response to a GAO report critical of handling of drone programs. Paul Scharre has reported that the cultural divide between the USAF and US Army has kept both services from adopting each other's drone handing innovations. Question: What is the reason for the shortage of UAV operators in the US Air Force?

Output: Cultural and career issues


Input: Consider Input: Passage: In 2009, the Internet Archive migrated its customized storage architecture to Sun Open Storage, and hosts a new data center in a Sun Modular Datacenter on Sun Microsystems' California campus. Question: When did Internet Archive chance its platform for data storage?


Output: 2009