TASK DEFINITION: Given a question and a context passage, generate the answer having the word or phrase from the context passage. Here, the answer should be a shortest continous span from the passage.
PROBLEM: Context: One of the primary criticismes of vestibular schwannoma (VS) radiosurgery is that the risk of surgical morbidity is increased for patients whose tumor progresses after the procedures. We reviewed the French experience of operated patients after failed Gamma Knife radiosurgery. From July 1992 to January 2002, 25 out of the 1000 treated patients underwent another treatment procedure for a gamma knife failure. Excluding the NF2 patients, 21 patients have been operated and the present study shows the data collected for 20 of them. In order to analyze the difficulties observed during the surgery, a questionnaire was filled by the surgeons. The mean interval between radiosurgery and removal was 36 Months, from 10 to 83 Months. The mean increase in Volume was 559% (37 to 3036%, median 160%). Evolution of the Koos grading was found from 8 grade II, 10 grade III et 2 grade IV to 10 grade III and 10 grade IV. Patients have been operated for radiological tumor growth in 7 cases and for clinico-radiological evolution in 13 cases. In 9 cases, the surgeon considered that he had to face unusual difficulties mainly because of adhesion of the tumor to neurovascular structures. Tumor removal was total in 14 cases, near total in 4 cases and subtotal in 2 cases. One case of venous infarction was noticed at the second day following surgery responsible of hemiparesis and aphasia that gradually recovered. At last follow-up examination, facial nerve was normal (House and Brackmann grade I and II) in 10 cases while it was a grade III in 7 cases and grade IV and V in 3 cases. We recommend that the decision for surgical removal of growing vestibular schwannoma after Gamma Knife treatment should be done after a sufficiently long follow-up period. Our results show that the quality of removal and of facial nerve preservation might be impaired by radiosurgery in half of cases. However these results do not support a change in our policy of radiosurgical treatment of small to medium size vestibular schwannoma. 
 Question: Which disease can be categorized using the Koos grading system?

SOLUTION: vestibular schwannoma

PROBLEM: Context: It seems that the Great Wall is the place to rock . There will be two parties held on the Great Wall this month. Great Wall I The latest Great Wall party is sponsored by the Club and Elektrobeat and held at Jinshanling. Local DJ Mark, as well as guests Slab from Australia, Usami and Bobby from Hong Kong will sing at the party. All drinks are priced at 20 yuan($ 2.4). Tickets: 200yuan($ 24), including bus ride there and back plus entrance fee to the Great Wall. T/D: 8p.m. to 2 a.m., Sept. 20. Pre-sale tickets are to be booked at: Public Space: 6416-0759; Neo Lounge: 6416-1077. Buses: Leave at 5 p.m. on Saturday, Sept. 20 from Neo Lounge, 99 Xinfuncun Zhonglu, Sanlitun, Chaoyang District. For more info: www. elektrobeat. com Great wall II The other party at the end of this month at Jinshanling will be started with live performances by Askar, Brain Failure, Longkuan, Supermarket, Mr. Zhou, Beijing Talking and the Yi band. Dance till dawn to the wonderful sounds of DJs Ben, Mickey Zhang, Will, Cheese, Gao Hu and Huang Weiwei. T/D: 8 p.m. to 2 a.m., Sept. 27. Tickets: 350 yuan ($ 42) or 300 yuan ($ 36) for groups of 10 or more, 500 yuan ($ 60) at the door and VIP tickets 800 yuan ($ 72), transportation included. Buses: Depart from the north gate of Wbrkers' Stadium at noon, 2 p.m., 4 p.m., Sept. 27. For more info: contact Li Zhenhua at lah@msgp. Org or call 133-2119-1731. 
 Question: What day of the week is September 27?

SOLUTION: saturday.

PROBLEM: Context: Billionaire Boy is a children's fiction book published on 28 October 2010 by HarperCollins and written by David Walliams and illustrated by Tony Ross. 
 Question: Who was Billionaire Boy illustrated by?

SOLUTION:
tony ross