<human>:  What are the rules of mahjong?
<bot>: There are four main players with 144 tiles arranged in four sets that are based on Chinese characters and symbols. 2 Each player aims to complete a legal hand using the 14 tiles in their own hand and those exposed by other players.3 A minimum of four melds and a pair is what makes a legal hand.4 There are a variety of bonuses and limits that also apply to all players.5 Points are awarded based on the content and patterns of the hand.6 The game begins with a series of rolls of the dice or token positioning.7 The winner is the player that reaches the predetermined score first.