P6177 - Cows and Primitive Roots

内存限制：256 MB 时间限制：2 S 标准输入输出

题目类型：传统评测方式：文本比较上传者：

提交：0 通过：0

The cows have just learned what a primitive root is! Given a prime p, a primitive root $\text{[math]}$ is an integer x (1≤x<p) such that none of integers x-1,x²-1,...,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 $\text{[math]}$ .

Input

The input contains a single line containing an integer p (2≤p<2000). It is guaranteed that p is a prime.

Output

Output on a single line the number of primitive roots $\text{[math]}$ .

Examples

Input

Output

Input

Output

Note

The only primitive root $\text{[math]}$ is 2.

The primitive roots $\text{[math]}$ are 2 and 3.

6177: Cows and Primitive Roots

题目描述