Leonardo Bonacci (c. 1175 – c. 1250]—known as Fibonacci (Italian), and Leonardo of Pisa, Leonardo Pisano Bigollo, Leonardo Fibonacci—was an Italian mathematician, considered to be "the most talented Western mathematician of the Middle Ages". Fibonacci popularized the Hindu–Arabic numeral system to the Western World primarily through his composition in 1202 of Liber Abaci (Book of Calculation). He also introduced Europe to the sequence of Fibonacci numbers, which he used as an example in Liber Abaci.