思路：找「右侧第一个 ≤ cur」的元素 → 弹出所有 cur 的元素，栈顶即为折扣。最终价格 = cur - 折扣（有则）或 cur（无则）。
It's also expensive and some environmental groups argue that emission reductions can be achieved at a lower cost, using more existing technology such as wind power, solar, and electric cars.
。业内人士推荐Line官方版本下载作为进阶阅读
“走出了一条中国特色减贫道路，形成了中国特色反贫困理论”
if the free list is scavanged. the general strategy is: