/in/foo.cc: In function 'void out(int, int, std::__cxx11::string&)':
/in/foo.cc:7:12: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     if (a+b>s.length())
         ~~~^~~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:20:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     if (a>s.length())
         ~^~~~~~~~~~~