foo.cc: In function 'int main()':
foo.cc:11:45: 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,j=s.length()-1;i<s.length()/2;i++,j--)
      |                                            ~^~~~~~~~~~~~~
foo.cc:28:45: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   28 |                 for(int i=0,j=s.length()-1;i<s.length()/2;i++,j--)
      |                                            ~^~~~~~~~~~~~~

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