The 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, x 2 - 1, ..., x p - 2 - 1 are divisible by p , but x p - 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 .

输入描述:

The input contains a single line containing an integer p(2 ≤ p . It is guaranteed that p is a prime.

输出描述:

Output on a single line the number of primitive roots .

备注:

The only primitive root is 2.The primitive roots are 2 and 3.