def binary_search(sorted_list, target):
    """Find where a number lies in a sorted list. Return lowest item
    that is greater than or equal to target, or None if no item
    in list greater than or equal to target
    """
    if sorted_list==[]:
        return None
    if len(sorted_list)==1:
        if target <= sorted_list[0]:
            return 0
        return None
    mid_index = int(len(sorted_list)/2)-1
    mid_value = sorted_list[mid_index]
    if target <= mid_value:
        return binary_search(sorted_list[0:mid_index+1], target)
    else:
        return mid_index + 1 + binary_search(sorted_list[mid_index+1:], target)