foo.c: In function 'compare':
foo.c:43:6: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
  if (i = n)
      ^
foo.c: In function 'main':
foo.c:12:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%c", &a[0]);
  ^~~~~~~~~~~~~~~~~~
foo.c:16:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%c", &a[i]);
   ^~~~~~~~~~~~~~~~~~
foo.c: In function 'compare':
foo.c:45:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^

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