对输入合式公式（例如P->Q）并能转化为波兰式（->PQ）和逆波兰式（PQ->），程序简单、操作容易，是个练手的小程序-The input formed formulas (such as P-> Q) and can be converted into Polish (-> PQ) and Reverse Polish Notation (PQ-> ), the program is simple, easy to operate, is a small pr