/in/foo.cc: In function 'void Unique()':
/in/foo.cc:30:8: error: 'head1' was not declared in this scope
     p1=head1;
        ^~~~~
/in/foo.cc:31:8: error: 'head2' was not declared in this scope
     p2=head2;
        ^~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:70:23: error: too many arguments to function 'void Unique()'
     Unique(head1,head2);
                       ^
/in/foo.cc:25:6: note: declared here
 void Unique()
      ^~~~~~
/in/foo.cc:71:23: error: too many arguments to function 'void Unique()'
     Unique(head1,head3);
                       ^
/in/foo.cc:25:6: note: declared here
 void Unique()
      ^~~~~~