def czech_long_numbers(input)
      input.gsub(/\d{5,}/) { |n| n.reverse.scan(/(.{1,3})/).join(' ').reverse }
    end
def czech_long_numbers(input)
      input.gsub(/\d{5,}/) { |n| n.reverse.scan(/(.{1,3})/).join(' ').reverse }
    end
Divides long numbers into parts of three digits using thin space.

 @param input [String] The paragraph which will be converted.
 @return [String] Paragraph with spaces inside of long numbers.