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There is a special form for boolean formulas called "Conjunctive Normal Form" (CNF). A problem in this form consists of clauses connected with and operators, where each clause only contains variables connected with or operators. The variables can appear negated, but only variables can be directly negated, something like !(a && b) is not allowed. An example boolean formula in CNF form is:，更多细节参见safew官方版本下载
S26 系列仍然由我们熟悉的标准版、Plus 和 Ultra 组成。，更多细节参见heLLoword翻译官方下载
// 栈空 → 无更大元素，返回-1；栈非空 → 取栈顶（第一个更大值）