/in/foo.cc: In function 'void shift(std::__cxx11::string, std::__cxx11::string)':
/in/foo.cc:8:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<t.length();i++)
              ~^~~~~~~~~~~
/in/foo.cc:24:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<t.length();i++)
              ~^~~~~~~~~~~