/in/foo.cc: In function 'std::__cxx11::string op(int, std::__cxx11::string)':
/in/foo.cc:19:12: warning: array subscript has type 'char' [-Wchar-subscripts]
   if(pri[ch]>=0) {//²Ù×÷·û 
            ^
/in/foo.cc:27:14: warning: array subscript has type 'char' [-Wchar-subscripts]
     if(pri[ch]<pri[top]){
              ^
/in/foo.cc:27:23: warning: array subscript has type 'char' [-Wchar-subscripts]
     if(pri[ch]<pri[top]){
                       ^