foo.cc: In function ‘int main()’:
foo.cc:17:31: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::__cxx11::basic_string<char>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   17 |                 for (int j=0;j<=ans.size()-1;j++)
      |                              ~^~~~~~~~~~~~~~