/in/foo.cc: In function 'int main()':
/in/foo.cc:104:16: warning: unused variable 'x' [-Wunused-variable]
  104 |         int n, x;
      |                ^
In member function 'void PolyLinkList::add(PolyLinkList&)',
    inlined from 'void PolyLinkList::mul(PolyLinkList&)' at /in/foo.cc:81:11,
    inlined from 'int main()' at /in/foo.cc:119:8:
/in/foo.cc:41:19: warning: 'acc.PolyLinkList::head' may be used uninitialized [-Wmaybe-uninitialized]
   41 |                 p = head, q = P.head;
      |                 ~~^~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:73:30: note: 'acc' declared here
   73 |                 PolyLinkList acc, temp;
      |                              ^~~