设计一个计数器类Calculator，它只有一个用于计数的数据成员count。该计数器的有效计数范围是0~65535，实现计时器的前自增，后自增，前自减，后自减，两个计数器的相加减等运算-Design a counter class Calculator, it has only one for the count data member count. The counter counts the effective range is 0 ~ 65535, before the realization of the timer increment after increment, the former since the reduction after self-subtraction, two counter-phase operations such as addition and subtraction