decimal IO；only contain ‘+’‘-’‘*’‘/’
The program can input, calculate and output the final result for mathematical expressions where the calculation result (including intermediate result and final result) is within 8 bits and there is at most one division operation in each monomial. And can make a simple judgment on the compliance of the input expression.
程序能针对计算结果（包括中间结果和最终结果）在8位内且各单项式中至多有一次除法运算的数学表达式，进行输入、计算和最终结果的输出。并能对输入表达式的合规性做简单的判断。