/in/foo.cc: In function 'int main()':
/in/foo.cc:16:28: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   16 |         for(long long i=1;i<a.size();i++)
      |                           ~^~~~~~~~~