/in/foo.cc: In function 'std::__cxx11::string decrypt(std::__cxx11::string, std::__cxx11::string)':
/in/foo.cc:6:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < B.length(); i++) {
                     ~~^~~~~~~~~~~~
/in/foo.cc:8:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         while (pos != string::npos) {
                ~~~~^~~~~~~~~
/in/foo.cc:17:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < A.length(); i++) {
                     ~~^~~~~~~~~~~~