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）。
Equal (2): Everything in this space must be equal to 2. The answer is 2-6, placed vertically; 2-1, placed horizontally.
，更多细节参见safew官方版本下载
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Over time, as people are uprooted from their agricultural communities as industrialisation tears apart people's familiar attachments, individuals become "alienated", he says. "They start looking for one other individual to save them, to save them from the wretchedness of their lives."