f(n) = \begin{cases} n/2 & \quad \text{if } n \text{ is even} \\ -(n+1)/2 & \quad \text{if } n \text{ is odd}\\ \end{cases}
表示: \[ f(n) = \begin{cases} n/2 & \quad \text{if } n \text{ is even} \\ -(n+1)/2 & \quad \text{if } n \text{ is odd}\\ \end{cases} \]