text: def binary_search(element, some_list):
      # 코드를 작성하세요.
      start_index = 0
      end_index = len(some_list) - 1
      while (start_index <= end_index):
          mid_index = (end_index + start_index) // 2
          if(some_list[mid_index] == element):
              return mid_index
          elif(some_list[mid_index] < element):
              start_index = mid_index + 1
          else:
              end_index = mid_index - 1
      return None
  
  print(binary_search(2, [2, 3, 5, 7, 11])) # 0
  print(binary_search(0, [2, 3, 5, 7, 11])) # None
  print(binary_search(5, [2, 3, 5, 7, 11])) # 2
  print(binary_search(3, [2, 3, 5, 7, 11])) # err
  print(binary_search(11, [2, 3, 5, 7, 11]))