foo.cc: In function 'int main()':
foo.cc:16:64: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   16 |                 for (int i = nums.size() - 1, u = 0; i >= 0, u < nums.size(); i--, u++)
      |                                                              ~~^~~~~~~~~~~~~
foo.cc:16:56: warning: left operand of comma operator has no effect [-Wunused-value]
   16 |                 for (int i = nums.size() - 1, u = 0; i >= 0, u < nums.size(); i--, u++)
      |                                                      ~~^~~~

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