foo.cc: In function ‘void get(std::string, int*)’:
foo.cc:5:18: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::__cxx11::basic_string<char>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
    5 |     for(int i=1;i<=n.size();i++)nn[i]=n[n.size()-i]-'0';
      |                 ~^~~~~~~~~~