foo.cc: In function 'void solve()':
foo.cc:37:34: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   37 |         for (int i = 0, j = 0; i < r.size() && j < b.size(); )
      |                                ~~^~~~~~~~~~
foo.cc:37:50: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   37 |         for (int i = 0, j = 0; i < r.size() && j < b.size(); )
      |                                                ~~^~~~~~~~~~

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