foo.cc: In function 'std::vector<int> findAns(std::vector<int>, std::vector<int>)':
foo.cc:9:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < index.size(); i = i + 2) {
                  ~~^~~~~~~~~~~~~~
foo.cc:10:13: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   if (i + 1 >= index.size()) {
       ~~~~~~^~~~~~~~~~~~~~~

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