def common_array(ary) # rubocop: disable AbcSize
      return ary unless ary.is_a? Array
      count = ary.count
      return ary if count.zero?
      return ary.flatten.uniq if count == 1
      common = ary[0] & ary[1]
      return common if count == 2
      (count - 2).times { |x| common &= ary[x + 2] } if count > 2
      common
    end
def common_array(ary) # rubocop: disable AbcSize
      return ary unless ary.is_a? Array
      count = ary.count
      return ary if count.zero?
      return ary.flatten.uniq if count == 1
      common = ary[0] & ary[1]
      return common if count == 2
      (count - 2).times { |x| common &= ary[x + 2] } if count > 2
      common
    end
=> Return Common Elements of an Array