foo.cc: In function 'int main()':
foo.cc:7:33: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
    7 |         for(i=0,j=a.length()-1;i<=a.length()/2;i++,j--)
      |                                ~^~~~~~~~~~~~~~
foo.cc:14:12: warning: 'n' may be used uninitialized [-Wmaybe-uninitialized]
   14 |         }}n++;
      |           ~^~

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