Euclid algorithm, also known as division by turns, is used to calculate the greatest common divisor of two positive integers A and B.

Background of Euclid algorithm:

As we know, around 300 BC, Euclid, a famous mathematician in ancient Greece, wrote a masterpiece "The Elements of Geometry", which almost covered all the contents of plane geometry and solid geometry learned in primary and secondary schools. Such an ancient geometric content has naturally become the focus of previous mathematics curriculum reforms. One of the most radical, such as Diodoni, the main figure of the French Bourbaki School, even shouted the slogan "Get out of Euclid". However, some contents of Euclidean geometry still constitute the main contents of mathematical geometry in primary and secondary schools in most countries. Some people call it the "tumbler phenomenon".