foo.cc: In function 'void Mul(std::vector<int>&, int)':
foo.cc:7:24: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
    7 |         for (int i=0; i<val.size(); i++)
      |                       ~^~~~~~~~~~~
foo.cc: In function 'void Mul(std::vector<int>&, std::vector<int>&, std::vector<int>&)':
foo.cc:23:24: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   23 |         for (int i=0; i<x.size(); i++)
      |                       ~^~~~~~~~~
foo.cc:24:32: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   24 |                 for (int j=0; j<y.size(); j++)
      |                               ~^~~~~~~~~
foo.cc:27:24: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   27 |         for (int j=0; j<ans.size(); j++)
      |                       ~^~~~~~~~~~~

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