foo.cc: In function 'int main()':
foo.cc:29:30: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<st>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   29 |                 for(int i=0;i<nt[x].size();i++)
      |                             ~^~~~~~~~~~~~~

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