foo.cc: In function 'BigInt operator*(BigInt&, int)':
foo.cc:22:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   22 |   for (int i = 0; i < A.v.size() || t; i++)
      |                   ~~^~~~~~~~~~~~
foo.cc:24:10: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   24 |    if (i < A.v.size())t += A.v[i] * b;
      |        ~~^~~~~~~~~~~~

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