foo.cc: In function 'int main()':
foo.cc:10:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
10 | for (int i = 0; i < s.size(); i++) {
| ~~^~~~~~~~~~
foo.cc:14:16: warning: comparison of integer expressions of different signedness: 'std::stack<char>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
14 | if (z.size() > ans) ans = z.size();
| ~~~~~~~~~^~~~~
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