/in/foo.cc: In member function 'BigInt BigInt::operator+(const BigInt&) const':
/in/foo.cc:24:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         while (i < digits.size() || j < other.digits.size()) {
                ~~^~~~~~~~~~~~~~~
/in/foo.cc:24:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         while (i < digits.size() || j < other.digits.size()) {
                                     ~~^~~~~~~~~~~~~~~~~~~~~
/in/foo.cc:26:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             if (i < digits.size()) {
                 ~~^~~~~~~~~~~~~~~
/in/foo.cc:30:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             if (j < other.digits.size()) {
                 ~~^~~~~~~~~~~~~~~~~~~~~
/in/foo.cc: In member function 'BigInt BigInt::operator*(const BigInt&) const':
/in/foo.cc:45:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int i = 0; i < digits.size(); i++) {
                         ~~^~~~~~~~~~~~~~~
/in/foo.cc:47:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             for (int j = 0; j < other.digits.size(); j++) {
                             ~~^~~~~~~~~~~~~~~~~~~~~