/in/foo.cc: In function 'int main()':
/in/foo.cc:32:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   32 |     while (start < stk.size() && stk[start] == '0') {
      |            ~~~~~~^~~~~~~~~~~~
/in/foo.cc:36:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   36 |     if (start == stk.size()) {
      |         ~~~~~~^~~~~~~~~~~~~
/in/foo.cc:39:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   39 |         for (int i = start; i < stk.size(); i++) {
      |                             ~~^~~~~~~~~~~~