foo.cc: In member function 'BigInt BigInt::operator*(const BigInt&) const':
foo.cc:52:17: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   52 |   for (i = 0; i < this->nu.size(); i++)
      |               ~~^~~~~~~~~~~~~~~~~
foo.cc:53:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   53 |    for (j = 0; j < rhs.nu.size(); j++)
      |                ~~^~~~~~~~~~~~~~~

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