def bSearch(lst,Val):

    def _binarySearch(lst, Low, High, Target):
        if Low > High:
            return -1
        Mid = (Low + High) // 2 #求序列中间位置
        if Target == lst[Mid]:
            return Mid
        elif Target < lst[Mid]: #如目标值小于中间元素，在左半部分查找
            return _binarySearch(lst, Low, Mid - 1, Target)
        else: #如目标值大于中间元素，在右半部分查找
            return _binarySearch(lst, Mid + 1, High, Target)

    return _binarySearch(lst,0,len(lst),Val)