In ancient China , values for π included (around 1 AD), √ 10 (100 AD, approximately ), and 142 / 45 (3rd century, approximately ).  Around 265 AD, the Wei Kingdom mathematician Liu Hui created a polygon-based iterative algorithm and used it with a 3,072-sided polygon to obtain a value of π of .   Liu later invented a faster method of calculating π and obtained a value of with a 96-sided polygon, by taking advantage of the fact that the differences in area of successive polygons form a geometric series with a factor of 4.  The Chinese mathematician Zu Chongzhi , around 480 AD, calculated that π ≈ 355 / 113 (a fraction that goes by the name Milü in Chinese), using Liu Hui's algorithm applied to a 12,288-sided polygon. With a correct value for its seven first decimal digits, this value of ... remained the most accurate approximation of π available for the next 800 years.