foo.cc: In function 'int main()':
foo.cc:11:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
11 | for (int i = 0; i < s.length(); i++)
| ~~^~~~~~~~~~~~
foo.cc:16:18: warning: comparison of integer expressions of different signedness: 'std::stack<char>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
16 | if (st.size() > maxdep)
| ~~~~~~~~~~^~~~~~~~
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