Input: Article: There are a number of aids available to pilots, though not all airports are equipped with them. A visual approach slope indicator (VASI) helps pilots fly the approach for landing. Some airports are equipped with a VHF omnidirectional range (VOR) to help pilots find the direction to the airport. VORs are often accompanied by a distance measuring equipment (DME) to determine the distance to the VOR. VORs are also located off airports, where they serve to provide airways for aircraft to navigate upon. In poor weather, pilots will use an instrument landing system (ILS) to find the runway and fly the correct approach, even if they cannot see the ground. The number of instrument approaches based on the use of the Global Positioning System (GPS) is rapidly increasing and may eventually be the primary means for instrument landings.

Now answer this question: What instruments do pilots use to find the runway and fly the correct approach, even if they cannot see the ground?

Output: instrument landing system

Input: Article: On 16 March 1934, President Franklin D. Roosevelt signed the Migratory Bird Hunting Stamp Act, which requires an annual stamp purchase by all hunters over the age of sixteen. The stamps are created on behalf of the program by the US Postal Service and depict wildlife artwork chosen through an annual contest. They play an important role in habitat conservation because ninety-eight percent of all funds generated by their sale go directly toward the purchase or lease of wetland habitat for protection in the National Wildlife Refuge System.[citation needed] In addition to waterfowl, it is estimated that one third of the nation's endangered species seek food and shelter in areas protected using Duck Stamp funds.[citation needed]

Now answer this question: What do 98% of all the funds generated by the stamp sales go to?

Output: the purchase or lease of wetland habitat

Input: Article: Charleston annually hosts Spoleto Festival USA founded by Gian Carlo Menotti, a 17-day art festival featuring over 100 performances by individual artists in a variety of disciplines. The Spoleto Festival is internationally recognized as America's premier performing arts festival. The annual Piccolo Spoleto festival takes place at the same time and features local performers and artists, with hundreds of performances throughout the city. Other festivals and events include Historic Charleston Foundation's Festival of Houses and Gardens and Charleston Antiques Show, the Taste of Charleston, The Lowcountry Oyster Festival, the Cooper River Bridge Run, The Charleston Marathon, Southeastern Wildlife Exposition (SEWE), Charleston Food and Wine Festival, Charleston Fashion Week, the MOJA Arts Festival, and the Holiday Festival of Lights (at James Island County Park), and the Charleston International Film Festival.

Now answer this question: How many days does the Spoleto Festival USA run each year?

Output:
17