#var1
def drop_list(all_list):
    example_set=set(all_list)
    all_set = set(list(range(all_list[0], all_list[-1])))
    return sorted(list(all_set - example_set))

#var2
def drop_list(all_list):
    droped_list =[]
    for number in range(all_list[0], all_list[-1]):
        if number not in all_list:
            droped_list.append(number)
    return droped_list