foo.cc: In function 'int main()':
foo.cc:76:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   76 |     for (int i = 0; i < image.size(); i++) {
      |                     ~~^~~~~~~~~~~~~~
foo.cc:77:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   77 |         for (int j = 0; j < image[i].size(); j++) {
      |                         ~~^~~~~~~~~~~~~~~~~

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