foo.cc: In function 'std::vector<int> mul(std::vector<int>&, int)':
foo.cc:14:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   14 |  for (int i = 0; i < A.size() || t; i ++ )
      |                  ~~^~~~~~~~~~
foo.cc:16:9: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   16 |   if (i < A.size()) t += A[i] * b;
      |       ~~^~~~~~~~~~

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