foo.cc: In function 'void Merge(Node*, Node*)':
foo.cc:57:30: warning: left operand of comma operator has no effect [-Wunused-value]
   57 |         for(p=head1,q=head2;p!=NULL,q!=NULL;)
      |                              ^
foo.cc: In function 'void Unique(Node*, Node*)':
foo.cc:114:18: warning: unused variable 'q' [-Wunused-variable]
  114 |         Node *p,*q;
      |                  ^
foo.cc: In function 'void FindMaxNeg(Node*)':
foo.cc:52:21: warning: 'x' may be used uninitialized [-Wmaybe-uninitialized]
   52 |         cout << x <<" ";
      |                     ^~~
foo.cc:37:13: note: 'x' was declared here
   37 |         int x;
      |             ^

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