foo.c: In function 'main':
foo.c:4:26: warning: unused variable 'c' [-Wunused-variable]
  int i, j, n, mid, a, b, c;
                          ^
foo.c:5:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &n);
  ^~~~~~~~~~~~~~~
foo.c:8:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d", &arr[c]);
   ^~~~~~~~~~~~~~~~~~~~

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