The mod function is a remainder function, and its format is: mod(nExp 1, nExp2), which is the remainder after dividing two numerical expressions. So: the remainder of two integers with the same sign is exactly the same as that of two positive integers you know (that is, the algorithm of two negative integers and two positive integers is the same), that is, the remainder of the division of two numbers is returned after the remainder of two numbers. Sqr(x) stands for the arithmetic square root of finding non-negative x Example: sqr(4) = 2.