#!/usr/bin/python
from sys import stdin

def magia (a, b):
   k = 2
   while k <= b:
      while a%k == 0 and b%k == 0:
         a = a/k
         b = b/k
      while a%k == 0: a = a/k
      k = k + 1
   return (b > 1)

def odpoved (n):
   vysledok = n+1
   skusam = n
   while skusam > 1:
      if magia (n, skusam): vysledok = skusam
      skusam = skusam - 1
   return vysledok - 1

N = int(stdin.readline())
body = 0
if 0 < N < 123456789012345: body = odpoved(N-1) / 2
print "Pocet bodov:", body