Question: The Battle of the Labyrinth is the fourth novel in a pentalogy of adventure and mythological fiction books that have sold more than 45 million copies, and have been sold in how many countries?
Context: Canadian singer Nelly Furtado has released six studio albums, twenty singles, one video album, one live album, two compilation albums, three extended plays, and twenty-three music videos.  Furtado released her debut album "Whoa, Nelly! " in 2000 and it became a commercial success selling 9 million copies worldwide.  It has been certified multi Platinum in countries such as Canada, United States, Australia and New Zealand.  The album spawned four singles including the successful top 10 hits; "I'm Like a Bird" and "Turn Off the Light".  In 2003 she released her second album "Folklore", while the album did not match the success of her previous album in such markets as the US and Australia, it did however become a success in several European countries.  "Folklore" has sold 3 million copies worldwide.  The album produced two European top 10 hits; "Powerless (Say What You Want)" and "Força", while "Try" peaked inside the top 10 in Canada.  Furtado's third album "Loose" (2006) became her best selling album of career with 12 million copies sold worldwide.  It also reached number one on the album chart of nine countries and was certified multi Platinum in several countries such as Canada, UK, Australia, Germany, Switzerland, Austria and New Zeeland.  The album spawned four successful number one singles; "Promiscuous", "Maneater", "Say It Right" and "All Good Things (Come to an End)".  "Loose" was one of the best selling albums of 2006–2007 and is twenty-second best-selling album of the 2000s.  She released her first Spanish language album "Mi Plan" in 2009 which became a success in Europe and on the Latin charts.  The lead single "Manos al Aire" became a European top 10 hit and also topped the "Billboard" Hot Latin Songs chart, making Furtado the first North American singer to reach number one on that chart with an original Spanish song.  "Mi Plan" has been certified Platinum (Latin) in the US.  In 2010 she released a remix album "Mi Plan Remixes" and her first greatest hits "The Best of Nelly Furtado".  Furtado released her fifth album "The Spirit Indestructible" in 2012, followed by "The Ride" in 2017. Encore (stylized as ƎNCORE) is the fifth studio album by American rapper Eminem.  It was released by Aftermath Entertainment, Shady Records, and Interscope Records.  Its release was set for November 16, 2004, but was moved up to November 12 (coincidentally, exactly eight years to the day since his debut album, "Infinite", was released) after the album was leaked to the Internet.  "Encore" sold 710,000 copies in its first three days, and went on to sell over 1.5 million copies in its first two weeks of release in the United States, certified quadruple-platinum that mid-December.  Nine months after its release, worldwide sales of the album stood at 11 million copies.  By December 2016, the album had sold over 5 million copies in the United States and more than 23 million copies worldwide. Percy Jackson & the Olympians, often shortened to Percy Jackson, is a pentalogy of adventure and mythological fiction books written by American author Rick Riordan, and the first book series in the Camp Half-Blood Chronicles.  Five supplementary books, along with three graphic novels, have also been released.  More than 45 million copies of the books have been sold in more than 35 countries. The Heroes of Olympus is a pentalogy of adventure, mythological fiction and fantasy novels by American author Rick Riordan that collectively form a sequel series to the "Percy Jackson & the Olympians" series.  This series details a conflict between Greek and Roman demigods and Gaea, the earth goddess.  Riordan introduces Roman mythology into his sequel series as well as several new characters.  The first book of the series, "The Lost Hero", was published on October 12, 2010.  The final entry in the series, "The Blood of Olympus", was published on October 7, 2014. The Battle of the Labyrinth is a 2008 fantasy-adventure novel based on Greek mythology; it is the fourth novel in the "Percy Jackson & the Olympians" series by Rick Riordan.  Percy Jackson, a fictional demigod (who is fifteen years old by the end of the book) attempts to stop Luke Castellan and his army from invading Camp Half-Blood through Daedalus's labyrinth by trying to convince the inventor not to give Ariadne's string to Luke. Jean Marie Auel ( ; "née" Untinen; born February 18, 1936) is an American writer who wrote the "Earth's Children" books, a series of novels set in prehistoric Europe that explores human activities during this time, and touches on the interactions of Cro-Magnon people with Neanderthals.  Her books have sold more than 45 million copies worldwide. Canadian singer Celine Dion has released twenty-six studio albums, seven live albums, seventeen compilation albums, and twenty-one box sets.  Her debut album, "La voix du bon Dieu" was issued in 1981.  In the '80s, Dion released her French-language albums in Canada, with several compilation albums issued also in France.  Her first English-language album, entitled "Unison" was released in 1990 and has sold over three million copies worldwide.  It was followed by "Dion chante Plamondon" in 1991 and "Celine Dion" in 1992.  The latter became one of six of her albums to be certified Diamond in Canada for shipments of at least one million units.  Dion's popularity became well-established with her 1993 album, "The Colour of My Love", which topped the charts in various countries, including the United Kingdom, Canada, and Australia, and has sold twenty million copies around the world.  In the United States, it was certified six-times platinum.  Released in 1995, "D'eux" became the best-selling French-language album in history, with sales of ten million copies worldwide.  In France alone, "D'eux" spent forty-four weeks at the top of the chart and has sold 4.5 million units, becoming the best-selling album of all time.  It also became Dion's first out of six Diamond-certified albums in France. The Kane Chronicles is a trilogy of adventure and Egyptian mythological fiction books written by American author Rick Riordan.  The series is set in the same universe as Riordan's "Percy Jackson & the Olympians", "The Heroes of Olympus", and "Magnus Chase and the Gods of Asgard". Seven Wonders is a pentalogy of children's fantasy, adventure and mythological fiction books written by American author Peter Lerangis.  It is based on Greek mythology and set around the Seven Wonders of the Ancient World.  Jack McKinley discovers a secret organization on a hidden island, and becomes the leader of a mission to retrieve seven lost magical orbs.  As Jack and his three friends realize their lives are at stake, they have no choice but to accept the quest and embark on the challenge. Ashok Kumar Banker (born 7 February 1964 in Mumbai, India) is an author and screenwriter.  His writing spans crime thrillers, essays, literary criticism, fiction and mythological retellings.  The author of several well-received novels including a trilogy billed as "India's first crime novels in English", he became widely known for his retellings of Indian mythological epics, starting with the internationally acclaimed and best-selling eight-volume Ramayana Series, which has been credited with the resurgence of mythology in Indian publishing.  "The New York Times" credited him with making mythology the most successful category in Indian publishing, describing his work as being "better written than many books in the genre that have followed – introduced the Ramayana to a new generation of readers."  His books have sold over 2 million copies and have been published in 16 languages in 58 countries.  His Epic India Library is an attempt to retell all the myths, legends and itihasa of the Indian sub-continent in one massive story cycle comprising over 70 volumes, "an epic library of India".  He is frequently nominated and shortlisted as one of India's top thinkers and celebrities.  The upcoming two-film adaptation of his Mahabharata is expected to be the biggest Indian film production to date.
Answer: 35