/in/foo.cc: In function 'void Output(std::vector<int>&)':
/in/foo.cc:6:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < a.size(); i++)
                     ~~^~~~~~~~~~
/in/foo.cc: In function 'void FindMin(std::vector<int>&)':
/in/foo.cc:14:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < a.size(); i++)
                     ~~^~~~~~~~~~