num = STDIN.gets.to_i

def check_prime(num)
  case num
  when 1 then
    false
  when 2 then
    true
  else
    (2..(num-1)).each do |index|
      if num % index == 0
        return false
      end
    end
    return true
  end
end

ans = 0
num.times do |n|
  ans += 1 if check_prime n
end

puts ans