/in/polynomial.cpp: In member function 'Polynomial Polynomial::operator*(const Polynomial&)':
/in/polynomial.cpp:85:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i <= this->degree; i++)
                  ~~^~~~~~~~~~~~~~~
/in/polynomial.cpp:87:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int j = 0; j <= that.degree; j++)
                   ~~^~~~~~~~~~~~~~