foo.cc: In function 'int main()':
foo.cc:13:17: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   13 |   for (i = 0; i < s.size(); i++)
      |               ~~^~~~~~~~~~
foo.cc:26:17: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   26 |   for (i = 0; i < s.size(); i++)
      |               ~~^~~~~~~~~~
foo.cc:31:17: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   31 |   for (i = 0; i < s.size(); i++)
      |               ~~^~~~~~~~~~

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