I was a Medieval mathematician. I was born in Pisa, but I grew up in North Africa, where I was exposed to the vast scientific and mathematical knowledge of the East. I was famous in my time for writing a book called the "Liber Abbaci," which introduced the decimal system to Europe and described how to do basic arithmetic with it. This was also the first time anyone in Europe had ever used a symbol for the number zero! However, you probably know me best for the series of numbers that begins 0, 1, 1, 2, 3, 5... I didn't invent it; I just borrowed it for a problem in my "Liber Abbaci." Who am I?