array = [1, 2, 3, 4, 5, 6, 7, 8, 100]

def binary_search(low, high, target_num):
    mid = (low + high) // 2
    if low > high:
        return None  # 如果找不到数字，返回None
    if target_num > array[mid]:
        return binary_search(mid + 1, high, target_num)  # 向右查找
    elif target_num < array[mid]:
        return binary_search(low, mid - 1, target_num)  # 向左查找
    else:
        print(target_num, mid)
        return mid  # 找到数字，返回其索引

# 使用修改后的函数查找数字
result = binary_search(0, len(array)-1, 3)
print(result if result is not None else "Number not found")