/in/foo.cc: In function 'std::string f(int)':
/in/foo.cc:6:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
    6 |         for(int i=0;i<s.size();i++){
      |                     ~^~~~~~~~~
/in/foo.cc:16:30: error: return-statement with no value, in function returning 'std::string' {aka 'std::__cxx11::basic_string<char>'} [-fpermissive]
   16 |                 if(s[i]=='E')return;
      |                              ^~~~~~
/in/foo.cc:19:1: warning: control reaches end of non-void function [-Wreturn-type]
   19 | }
      | ^