/in/foo.cc: In function 'bool canPass(const std::vector<std::vector<char> >&)':
/in/foo.cc:13:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   13 |         for (int j = 0; j < field[i].size(); ++j) {
      |                         ~~^~~~~~~~~~~~~~~~~
/in/foo.cc:26:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   26 |         for (int j = 0; j < field[i + 1].size(); ++j) {
      |                         ~~^~~~~~~~~~~~~~~~~~~~~