def binary_search(list, item):

     low = 0

     high = len(list)-1                         # Tracking list head and tail

     n = 0

     while low <= high:

         mid = int((low + high)/2)              #Take the middle number

         guess = list[mid]

         n += 1

         if list[mid]==item:

             print(n)

             return mid

         if list[mid]<item:                     #Change the head and tail pointers

             low = mid + 1

         else:

             high = (mid-1)

     return None

 m=[1,2,3,4,8,9,11,12,14,18,19,20,28]

 print(binary_search(m,14))