foo.c: In function 'Search':
foo.c:12:23: error: 'NU' undeclared (first use in this function); did you mean 'N'?
   12 |     while (current != NU)
      |                       ^~
      |                       N
foo.c:12:23: note: each undeclared identifier is reported only once for each function it appears in
foo.c: In function 'main':
foo.c:28:22: error: 'NU' undeclared (first use in this function); did you mean 'N'?
   28 |     struct N* head = NU;
      |                      ^~
      |                      N

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