foo.c: In function 'main':
foo.c:5:19: error: redeclaration of 'n' with no linkage
    5 |         int x,y,z,n;
      |                   ^
foo.c:4:13: note: previous declaration of 'n' with type 'int'
    4 |         int n;
      |             ^
foo.c:9:17: error: 'max' undeclared (first use in this function)
    9 |                 max=x;
      |                 ^~~
foo.c:9:17: note: each undeclared identifier is reported only once for each function it appears in
foo.c:5:19: warning: unused variable 'n' [-Wunused-variable]
    5 |         int x,y,z,n;
      |                   ^

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