284_A. Cows and Primitive Roots
The cows have just learned what a primitive root is! Given a prime p, a primitive root <image> 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 <image>.

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 <image>.

Examples

Input

3


Output

1


Input

5


Output

2

Note

The only primitive root <image> is 2.

The primitive roots <image> are 2 and 3.
```python
def f(n):
    m = 1
    for i in range(1,p-1):
        m = (m*n)%p
        if (m-1)%p:
            pass
        else:
            return False
    if (m*n-1)%p:
        return False
    return True
p = int(input())
ans = 0
for i in range(1,p):
    if f(i):
        ans += 1
print(ans)
```