Question: World Richi Championship is commonly played by how many players

Context paragraphs:
Last Empire-War Z: ""Last Empire - War Z "" is a popular freemium Massively Multiplayer Online strategy game developed and published by IM30 Studios.It was launched in August 2015 and then spread all over the world, it became popular among players with a shocking speed, now having over 80 million downloads and is available in over 220 countries.  It is the Google play“Best of Game 2016”. " "Last Empire- War Z"" has been recommended to globe twice and to districts for several times.  It always takes a high rank in App download list in most countries and is one of the best strategies games that was beloved by players.  High rates and good comments mean it attracting more and more worldwide players.However, despite the great success it has achieved, many players would complain about having difficulties dealing with all kinds of bug when enjoying the gameplay, and the constant ignoration from the game when trying to report the problems they have came up with.  It seems that more and more players have shown their dissatisfaction about the game itself as it always tend to release new updates in order to earn more money instead of responding to players or paying attention on solving the bugs.  Also, the game's system is almost the same as another strategy game - Clash of Kings.

Mahjong: Mahjong ( , ] ) is a tile-based game that originated in China during the Qing dynasty.  It is commonly played by four players (with some three-player variations found in South Korea and Japan).  The game and its regional variants are widely played throughout Eastern and South Eastern Asia and have a small following in Western countries.  Similar to the Western card game rummy, Mahjong is a game of skill, strategy, and calculation and involves a degree of chance.

World Riichi Championship: World Riichi Championship (WRC) is the worldwide competition of Mahjong under Japanese rule since 2014.  Both men and women are eligible to contest this title.  The competition is organized by the TNT French Riichi Mahjong Club mainly.

Canasta: Canasta ( ; Spanish for "basket") is a card game of the rummy family of games believed to be a variant of 500 Rum.  Although many variations exist for two, three, five or six players, it is most commonly played by four in two partnerships with two standard decks of cards.  Players attempt to make melds of seven cards of the same rank and "go out" by playing all cards in their hand.  It is the only partnership member of the family of Rummy games to achieve the status of a classic.

Top League: The Top League is a rugby union competition in Japan.  It is the highest level of rugby competition in the country and is an industrial league, where many players are employees of their company and the teams are all owned by major companies.  The competition is knowned for paying high salaries, however, only the world class foreign players and a small number of Japanese players make the professional contract which means that most of the players play in a amateur level.  The Japan Rugby Football Union created the competition in 2003, by absorbing the Japan Company Rugby Football Championship, to drive up the overall standard and popularity of the sport and improve the results of the Japan national rugby union team.  The first season in 2003–04 featured 12 teams.  The league was expanded to 14 teams in 2006–07 and 16 teams in 2013–14.

Sheepshead (game): Sheepshead or Sheephead is a trick-taking card game related to the Skat family of games.  It is the Americanized version of a card game that originated in Central Europe in the late 18th century under the German name "Schafkopf".  Sheepshead is most commonly played by five players, but variants exist to allow for two to eight players.  There are also many other variants to the game rules, and many slang terms used with the game.

Black Lady: Black Lady is an extremely combative variant of the card game Whist that is popular in the United Kingdom and is similar to the North American game Hearts.  It is commonly played among large groups of players, typically 8 to 10, using two decks of cards, or it can be played by as few as three players using a single deck.

Crab soccer: Crab soccer (American English and Australian English), or crab football (British English), is an informal sport played by two teams.  The objective is to kick an inflated ball into a goal to score points.  The game is commonly played in Physical education classes.  The game can be played with a regular soccer ball, but is often played with a cage ball.  At the end of the game, the team with the most points wins.  Unlike soccer, players support themselves on their hands and move with their feet, in motions that make them look like crabs, a method known as crab walking.  Crab soccer can be played either outdoors or in a gymnasium, and is more commonly thought of as being a sport mostly played by children.

Coupe de l'Espérance: The Coupe de l'Espérance was a rugby union competition that was played in France to replace the national championship during World War I, as many players were sent to the front.  The teams used mostly young boys who had not been drafted yet.  The cup was awarded only four times (1916-1919) and does not count as a full championship title among club honours.

Paper soccer: Paper soccer (or paper hockey) is an abstract strategy game played on a square grid representing a soccer or hockey field.  Two players take turns to extend a line representing the position of a ball, until it reaches one of the grid's two goal spaces.  A traditional paper-and-pencil game, it is commonly played in schools and can be found in children's magazines.  Many computer implementations of the game also exist.  Despite the game's simple rules, paper soccer has several expanded strategies and tactics.

Supporting paragraphs: World Riichi Championship Mahjong
Answer: four