foo.cc: In function 'int main()':
foo.cc:52:21: warning: ISO C++ forbids converting a string constant to 'char*' [-Wwrite-strings]
   52 |         char * op = "+-*/()#";
      |                     ^~~~~~~~~
foo.cc:66:14: warning: comparison of integer expressions of different signedness: 'int' and 'const std::__cxx11::basic_string<char>::size_type' {aka 'const long unsigned int'} [-Wsign-compare]
   66 |          if(a==string::npos) break;
      |             ~^~~~~~~~~~~~~~
foo.cc: In function 'int Judge(char, char)':
foo.cc:27:1: warning: control reaches end of non-void function [-Wreturn-type]
   27 | }
      | ^

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