Task: Question Answering
Input (English): Passage: Karluk had been chosen by Pedersen and bought by Stefansson for the bargain price of US$10,000. Stefansson was advised by Pedersen that, of four ships that were available, Karluk was "the soundest and best adapted for our purpose", but Bartlett had deep reservations about her fitness for prolonged Arctic service. The ship, a 29-year-old brigantine, was 129 feet (39 m) in length with a beam of 23 feet (7.0 m). She had been built for the Aleutian fishing industry (karluk is the Aleut word for "fish") and later converted for whaling, when her bows and sides had been sheathed with 2-inch (51 mm) Australian ironwood. Despite 14 arctic whaling voyages, including six overwinterings, she had not been built to withstand sustained ice pressure, and lacked the engine power to force a passage through the ice. She did not match the expectations of Bartlett, or of many of the more experienced crew.The ship spent most of April and May 1913 undergoing repairs and refitting at the dockyard in Esquimalt. When Bartlett arrived in early June he immediately ordered further repair work. In addition to Karluk, Stefansson had purchased sight unseen a small gasoline-driven schooner, Alaska, to act as a supply ship for the Southern Party. He later added a second schooner, Mary Sachs, when the hold space in Alaska proved inadequate. In the confusion surrounding the expedition's departure, McKinlay notes, no attempt was made to align men or equipment to their appropriate ships. Thus anthropologists Henri Beuchat and Diamond Jenness, both designated for the Southern Party, found themselves sailing with Karluk, while their equipment was on board Alaska. McKinlay himself, aboard Karluk as magnetic observer, discovered that most of his equipment was with Alaska. Stefansson insisted that all would be sorted out when the ships reached their Herschel Island rendezvous. "Heaven help us all if we failed to reach Herschel Island", McKinlay wrote. 
Question: What were the names of the three ships bought by Stefansson?
Output (English): Mary Sachs.