/in/foo.cc: In function 'std::string mul(std::string, std::string)':
/in/foo.cc:68:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::deque<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   68 |         for (int i = 0; i < num2.size(); i++)
      |                         ~~^~~~~~~~~~~~~
/in/foo.cc:70:35: warning: comparison of integer expressions of different signedness: 'int' and 'std::deque<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   70 |                 for (int j = 0; j < num1.size() || carry !=0; j++)
      |                                 ~~^~~~~~~~~~~~~
/in/foo.cc: In function 'std::string sub(std::string, std::string)':
/in/foo.cc:99:35: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   99 |                 for (int i = 0; i < s1.size(); i++)
      |                                 ~~^~~~~~~~~~~
/in/foo.cc:120:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  120 |         for (int i = 0; i < s1.size(); i++)
      |                         ~~^~~~~~~~~~~
/in/foo.cc: In function 'int compare(std::string, std::string)':
/in/foo.cc:156:35: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  156 |                 for (int i = 0; i < s1.size(); i++)
      |                                 ~~^~~~~~~~~~~
/in/foo.cc: In function 'std::string div(std::string, std::string, int)':
/in/foo.cc:194:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  194 |         for (int i = 0; i < s1.size(); i++)
      |                         ~~^~~~~~~~~~~
/in/foo.cc:227:1: warning: control reaches end of non-void function [-Wreturn-type]
  227 | }
      | ^