A. Cows and Primitive Rootstime limit per test2 secondsmemory limit per test256 megabytesinputstandard inputoutputstandard outputThe cows have just learned what a primitive root is! Given a prime p, a primitive root  is an integer x (1 ≤ x < p) such that none of integers x - 1, x2 - 1, ..., xp - 2 - 1 are divisible by p, but xp - 1 - 1 is. Unfortunately, computing primitive roots can be time consuming, so the cows need your help. Given a prime p, help the cows find the number of primitive roots .InputThe input contains a single line containing an integer p (2 ≤ p < 2000). It is guaranteed that p is a prime.OutputOutput on a single line the number of primitive roots .ExamplesInput3Output1Input5Output2NoteThe only primitive root  is 2.The primitive roots  are 2 and 3.
Input3
Output1
['implementation', 'math', 'number theory', '*1400']