foo.cc: In function 'std::string jz(long long int)':
foo.cc:18:22: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   18 |         for(int i=0;i<ret.size();i++)
      |                     ~^~~~~~~~~~~
foo.cc: In function 'bool hw2(std::string)':
foo.cc:38:35: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   38 |         for(int i=0,j=s.size()-1;i<s.size();i++,j--)
      |                                  ~^~~~~~~~~

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