Problem:
Score: 200 points

Problem Statement

The number 105 is quite special - it is odd but still it has eight divisors.
Now, your task is this: how many odd numbers with exactly eight positive divisors are there between 1 and N (inclusive)?

Constraints

N is an integer between 1 and 200 (inclusive).

Input

Input is given from Standard Input in the following format:

N

Output

Print the count.

Sample Input 1

105

Sample Output 1

1

Among the numbers between 1 and 105, the only number that is odd and has exactly eight divisors is 105.

Sample Input 2

7

Sample Output 2

0

1 has one divisor. 3, 5 and 7 are all prime and have two divisors. Thus, there is no number that satisfies the condition.

Solution in Ruby (2.7.1) (judge verdict: Accepted)

require 'set'

def calc_d(n)
  i = 1
  d = Set.new
  while i ** 2 <= n
    if n % i == 0
      d << i
      d << n / i    
    end
    i += 1
  end
  d.size
end

n = gets.to_i

ans = 0

1.upto(n) do |i|
  next if i % 2 == 0
  ans += 1 if calc_d(i) == 8
end

puts ans