Theorem 2 also known as the theorem of Fermi-Euler and fully sounds so:Any prime number the form 4k+1, where k is a natural number, can be presented as a sum of two squares of natural numbers, besides by only one possible way.Let's focus now on a problem, how to get decomposition of any prime 4k+1 to a sum of two squares.As I read in the internet, effective methods now allegedly do not exist.Most