foo.cc: In function ‘int main()’:
foo.cc:20:24: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<int>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   20 |                 if(maxa<a[i].size())
      |                    ~~~~^~~~~~~~~~~~
foo.cc:31:22: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<int>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   31 |         for(int i=0;i<a[maxi].size();i++)
      |                     ~^~~~~~~~~~~~~~~