# The way that Code.org teaches Recursive Binary Search

def binarySearch(nums, left, right, target):
    if left>right:
        return -1
    
    middle = (left+right)//2
    
    if target < nums[middle]:
        return binarySearch(nums,left, middle-1, target)
    elif target > nums[middle]:
        return binarySearch(nums,left+1, middle, target)
    else:
        return middle
    
    
test_list = [2,4,6,8,10,12,14,16,18,20]

result = binarySearch(test_list,0,len(test_list),6)
print(result)