/in/foo.cc: In member function 'int alu::isbig(std::__cxx11::string&, std::__cxx11::string&)':
/in/foo.cc:61:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 0; i < num1.size(); i++){
                 ~~^~~~~~~~~~~~~
/in/foo.cc: In member function 'std::__cxx11::string alu::_sub(std::__cxx11::string&, std::__cxx11::string&)':
/in/foo.cc:74:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (long long i = num2size;i < num1.size();i++)
                              ~~^~~~~~~~~~~~~