The cows have just learned what a primitive root is! Given a prime *p*, a primitive root <img align="middle" class="tex-formula" src="https://espresso.codeforces.com/f203bd9f1553a2d666452cec7d6f1f4f02a817fb.png" style="max-width: 100.0%;max-height: 100.0%;"/> is an integer *x* (1 ≤ *x* &lt; *p*) such that none of integers *x* - 1, *x*<sup class="upper-index">2</sup> - 1, ..., *x*<sup class="upper-index">*p* - 2</sup> - 1 are divisible by *p*, but *x*<sup class="upper-index">*p* - 1</sup> - 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 <img align="middle" class="tex-formula" src="https://espresso.codeforces.com/f203bd9f1553a2d666452cec7d6f1f4f02a817fb.png" style="max-width: 100.0%;max-height: 100.0%;"/>.
The input contains a single line containing an integer *p* (2 ≤ *p* &lt; 2000). It is guaranteed that *p* is a prime.
import math

'''
/*
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, 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 .
 
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 .
*/
'''

p = int(input())
ans = 0

for x in range(1, math.sqrt(p) + 1):
  valid = True
  power = 1
  for i in range(1, p - 2):
    power *= x

    if ((power - 1) % p == 0):
      valid = False
      break
  
  power *= x

  if (valid and (power - 1) % p == 0):
    ans += 1

print(ans)