/in/foo.cc: In function 'std::__cxx11::string decrypt(std::__cxx11::string, std::__cxx11::string)':
/in/foo.cc:9:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < A.length(); i++) {
                     ~~^~~~~~~~~~~~
/in/foo.cc:10:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         if (j < B.length() && A[i] == B[j]) {
             ~~^~~~~~~~~~~~