# 1. Initial Solution

def separate_comma(number)
array = []
counter = 0
output_string = ''
  # puts number.class
number = number.to_s
  # puts number.class
number.reverse!
  # puts number.class
array = number.split(//)

array.each do | i |
  if counter == 3
    output_string << ','
    output_string <<  i.to_s
    counter = 1
  else
    output_string << i.to_s
    counter += 1
    end
  end
  puts output_string.class
  return output_string.reverse
end