// 步骤3：从后往前遍历数组（反向遍历更易理解，每个元素只入栈/出栈一次）
the end of each business day, all of these slips (which basically constitute
。同城约会是该领域的重要参考
从一场场重要会议到一次次国内考察调研，习近平总书记的一系列重要论述，成为各地推进过渡期工作的根本遵循和力量源泉。
If you design your functions to fully consume their arguments then you simply reference (ref)
Less than: Every domino half in this space must add up to less than the number.