/in/foo.cc: In function 'Result Match(std::__cxx11::string&)':
/in/foo.cc:16:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0; i<s.length(); i++)
               ~^~~~~~~~~~~
/in/foo.cc:20:5: warning: suggest explicit braces to avoid ambiguous 'else' [-Wparentheses]
   if(s[i]==')')
     ^