foo.cc: In function 'bool solve(ll)':
foo.cc:112:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  112 |         for(int j=0; j<arv[i].size(); j++) {
      |                      ~^~~~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务