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 .
示例1

输入

3<br />5<br />

输出

1<br />2<br />

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