foo.cc: In function 'void turn(std::string)':
foo.cc:32:15: 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]
   32 |  for(int i=0;i<x.size();++i) {
      |              ~^~~~~~~~~

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