Question:  Lisa Smith-Batchen was the first American to win  Marathon des Sables a six day marathon that spans how long of a distance?

Context paragraphs:
Vancouver Marathon: The BMO Vancouver Marathon is an annual race held on the first Sunday of May each year in Vancouver, British Columbia, Canada.  As the second largest international marathon event in Canada, it has a certified running distance of 26 miles and 385 yards long.  The most recent marathon saw over 14,000 people participate on May 4, 2014, with over 3700 completing the marathon distance.  This marathon is certified by the International Association of Athletics Federations & Association of International Marathons and Distance Races as a qualifying marathon race.

Nikki Kimball: Nikki Kimball (born May 23, 1971) is an American distance runner specializing in the Ultramarathon.  She ran her first 100-mile race at the Western States 100 Mile Endurance Run in 2004, and was the female winner.  She was the winning female at Western States again in 2006 and 2007, becoming only the third woman to win Western States three times.  In 2014, she won the Marathon Des Sables multi-stage endurance race on her first attempt.  Prior to running, her main sport was cross-country skiing.  She was crewed at the 2007 Western States by U.S. Senator Max Baucus of Montana, where Kimball lives.  She lives in Bozeman, Montana.

Dima and Lama Hattab: Dima and Lama Hattab (born December 31, 1980) are twin sisters from Jordan best known for being the first female ultramarathon runners in the Middle East to take part in the famous endurance race Marathon des Sables.  The Hattab twins also promote the sport of running in the Middle East, especially among women.  In cooperation with the World Humanitarian Marathon and Ultramarathon Foundation (WMHF), they organize the Jabal Isrhin marathon, a famous annual race that takes place in Jordan’s Wadi Rum.

Long Island Marathon: The Long Island Marathon is an annual marathon foot-race run on Long Island, New York, United States.  The 42.195 km event was first run in 1970 as "The Earth Day Marathon".  Originally the race consisted of loops around Roosevelt Raceway and Eisenhower Park in East Meadow, New York.

Lisa Smith-Batchen: Lisa Smith-Batchen is an ultramarathon runner and ironman competitor.  She was the first American to win Marathon des Sables.

Elijah Kemboi: Elijah Kiprono Kemboi (born 1984) is a Kenyan long-distance runner who competes in marathon races.  He has won marathons in Košice and Antwerp.  His personal best for the event is 2:07:34 hours.  He competed in Kenyan road races in his early twenties and the Nairobi Marathon was his first experience of the distance (14th in 2008 and 21st in 2009).  It was not until 2011 that he started racing at the top level in European marathons.  That year saw him win the Antwerp Marathon in a course record time of 2:11:15 hours.  He matched that time to win the Košice Peace Marathon in October.  The following year he was tenth at the Barcelona Marathon (2:12:15), but was much improved on his return to Košice: although he failed to defend his title and ended the race in fourth, he set a new lifetime best of 2:07:51 hours for the distance.

Meb Keflezighi: Mebrahtom "Meb" Keflezighi ( ; Ge'ez: መብራህቶም ክፍልእዝጊ, "Mebrāhtōm Kifl'izgī"; born May 5, 1975) is an Eritrean-born American long distance runner.  He is the 2004 Olympic silver medalist in the marathon and finished in fourth place in the 2012 Summer Olympics.  He won the 2009 New York City Marathon on November 1, 2009, and the 2014 Boston Marathon on April 21, 2014, becoming the first American man to win each race since 1982 and 1983, respectively.  Keflezighi is a graduate of UCLA where he won four NCAA championships competing for the UCLA Bruins track and field team.  He came in fourth in the 2014 New York City Marathon on November 2, 2014, eighth in the 2015 Boston Marathon on April 20, 2015 and second in the 2016 U.S. Olympic Team Trials to qualify for the 2016 Summer Olympics.

French Riviera Marathon: The French Riviera Marathon (French: "Marathon Des Alpes-Maritimes" ) is a marathon held annually along the south east coast of France, between the cities of Nice and Cannes.  The event was first held in 2008, when the race achieved its full capacity of 10,000 runners, setting a new world record attendance for an event on its debut.  Although the race has only been competed since 2008, it trails only the Paris Marathon in terms of participation within France.  In 2013, it was listed as an IAAF Bronze Label Road Race for the first time, a status it retained in 2014.

Camille Herron: Camille Herron (born December 25, 1981) is an American long-distance runner from Oklahoma City, OK.  She is the 2017 Comrades Marathon Champion and the first American to win since 1997.  She is a three-time Olympic Marathon Trials qualifier, 20-time marathon winner, Guinness World Record holder for the fastest marathon in a Superhero costume, and currently aiming to become the first woman to win a marathon in all 50 US States.  She won the 2015 USATF 100K National Championship at Mad City in 7:26:24, her debut at the distance.  She also became the first 3-time winner of the Oklahoma City Memorial Marathon.  She won the 2015 IAU 100K World Championships with a personal best 7:08:35.  In October 2015 she set a new "World Road Best" for 50 Miles at the Fall 50/US 50 Mile Road Championship running a time of 5:38:41 on the USATF Certified and Sanctioned course.  In December 2015, she won the 1st IAU 50 km World Championships in Doha, Qatar in a time of 3:20:58.

Marathon des Sables: Marathon des Sables, or MdS, (French for Marathon of the Sands, also known as Sahara Marathon) is a six-day, 251 km ultramarathon, which is approximately the distance of six regular marathons.  The longest single stage (2009) is 91 km long.

Supporting paragraphs: Lisa Smith-Batchen Marathon des Sables
Answer: 251 km ultramarathon