/in/foo.cc: In member function 'BigInteger BigInteger::operator=(const BigInteger&)':
/in/foo.cc:43:27: 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 'BigInteger BigInteger::operator+(const BigInteger&) const':
/in/foo.cc:54:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             if (g == 0 && i >= s.size() && i >= b.s.size()) {
                           ~~^~~~~~~~~~~
/in/foo.cc:54:46: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             if (g == 0 && i >= s.size() && i >= b.s.size()) {
                                            ~~^~~~~~~~~~~~~
/in/foo.cc: In member function 'BigInteger BigInteger::operator-(const BigInteger&) const':
/in/foo.cc:75:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             if (g == 0 && i >= s.size() && i >= b.s.size()) {
                           ~~^~~~~~~~~~~
/in/foo.cc:75:46: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             if (g == 0 && i >= s.size() && i >= b.s.size()) {
                                            ~~^~~~~~~~~~~~~
/in/foo.cc:80:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             if (i < s.size()) {
                 ~~^~~~~~~~~~
/in/foo.cc:83:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             if (i < b.s.size()) {
                 ~~^~~~~~~~~~~~
/in/foo.cc: In member function 'bool BigInteger::operator==(const BigInteger&) const':
/in/foo.cc:117:27: 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/(int) const':
/in/foo.cc:179:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int i = 0; i < s.size(); i++) {
                         ~~^~~~~~~~~~
/in/foo.cc: In function 'std::ostream& operator<<(std::ostream&, const BigInteger&)':
/in/foo.cc:195:43: error: 'strlen' was not declared in this scope
             for (int j = 0; j < strlen(buf); j++) {
                                           ^