foo.cc: In member function 'void gjd::Add(std::vector<int>&)':
foo.cc:30:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   while(i<v.size()&&i<v2.size())
         ~^~~~~~~~~
foo.cc:30:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   while(i<v.size()&&i<v2.size())
                     ~^~~~~~~~~~
foo.cc:37:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   while(i<v.size())
         ~^~~~~~~~~
foo.cc:44:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   while(i<v2.size())
         ~^~~~~~~~~~
foo.cc: In member function 'void gjd::Sub(std::vector<int>)':
foo.cc:60:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   while(i<v.size()&&i<v1.size())
         ~^~~~~~~~~
foo.cc:60:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   while(i<v.size()&&i<v1.size())
                     ~^~~~~~~~~~
foo.cc: In member function 'void gjd::Mul(int)':
foo.cc:80:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   while(i<v.size())
         ~^~~~~~~~~

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