foo.cc: In function 'Node* Merge(Node*, Node*)':
foo.cc:206:15: error: redeclaration of 'Node* tail'
  206 |         Node* tail = newhead;
      |               ^~~~
foo.cc:188:15: note: 'Node* tail' previously declared here
  188 |         Node* tail = newhead;
      |               ^~~~

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