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## B - Same Parity Summands

### 思路与做法

$$n,k$$ 的奇偶性讨论有解情况

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## C - K-th Not Divisible byn

### 思路与做法

$$k\operatorname{mod}(n-1)>0$$

$\def\K{\lfloor\frac{k}{n-1}\rfloor} \def\arraystretch{1.5} \begin{array}{c:c:c:c:c|c} \color{green}1 & \color{green}2 & \color{green}... & \color{green}... & \color{green}n-1 & \color{red}n \\ \hdashline \color{green}n+1 & \color{green}n+2 & \color{green}... & \color{green}... & \color{green}2n-1 & \color{red}2n \\ \hdashline \color{green}\vdots & \color{green}\vdots & \color{green}... & \color{green}... & \color{green}\vdots & \color{red}\vdots \\ \hdashline \color{green}\K n+1 & \color{green}\K n+2 & \color{green}... & \color{green}\K n+ k\operatorname{mod}(n-1) & \end{array}$

$$k\operatorname{mod}(n-1)=0$$ 时，

$\def\K{\lfloor\frac{k}{n-1}\rfloor} \def\arraystretch{1.5} \begin{array}{c:c:c:c|c} \color{green}1 & \color{green}2 & \color{green}... & \color{green}n-1 & \color{red}n \\ \hdashline \color{green}n+1 & \color{green}n+2 & \color{green}... & \color{green}2n-1 & \color{red}2n \\ \hdashline \color{green}\vdots & \color{green}\vdots & & \color{green}\vdots & \color{red}\vdots \\ \hdashline \color{green}(\K-1) n+1 & \color{green}(\K-1) n+2 & \color{green}... & \color{green}\K n-1 & \color{red}\K n \end{array}$

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Alice 先手吃一块

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## G - Special Permutation

### 思路与做法

$$n<4$$ 时显然无解

$$n\geqslant4$$ 为奇数时我们可以这样构造

n n-2 ... 3 1 4 2 6 ... n-3 n-1

$$n\geqslant4$$ 为偶数时我们可以这样构造

n-1 n-3 ... 3 1 4 2 6 ... n-2 n

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