/in/foo.cc: In member function 'BigInteger BigInteger::operator=(const BigInteger&)':
/in/foo.cc:65:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int i = 0; i < b.s.size(); i++) {
                         ~~^~~~~~~~~~~~
/in/foo.cc: In member function 'bool BigInteger::operator==(const BigInteger&) const':
/in/foo.cc:109:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int i = 0; i < s.size(); i++) {
                         ~~^~~~~~~~~~
/in/foo.cc: In member function 'BigInteger BigInteger::operator-(const BigInteger&) const':
/in/foo.cc:212:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                 if (g == 0 && i >= sa.size() && i >= sb.size()) {
                               ~~^~~~~~~~~~~~
/in/foo.cc:212:51: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                 if (g == 0 && i >= sa.size() && i >= sb.size()) {
                                                 ~~^~~~~~~~~~~~
/in/foo.cc:217:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                 if (i < sa.size()) {
                     ~~^~~~~~~~~~~
/in/foo.cc:222:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                 if (i < sb.size()) {
                     ~~^~~~~~~~~~~
/in/foo.cc: In function 'std::ostream& operator<<(std::ostream&, const BigInteger&)':
/in/foo.cc:295:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             for(int j = 0; j < strlen(buf); j++) out << buf[j];
                            ~~^~~~~~~~~~~~~