foo.cc: In function ‘int main()’:
foo.cc:18:30: warning: comparison of integer expressions of different signedness: ‘long long int’ and ‘std::vector<long long int>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   18 |                 for(int k=0;k<g[i].size();k++)
      |                             ~^~~~~~~~~~~~