foo.c: In function 'main':
foo.c:7:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    7 |  scanf("%d",&n);
      |  ^~~~~~~~~~~~~~
foo.c:9:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    9 |   scanf("%d",&a[i]);
      |   ^~~~~~~~~~~~~~~~~
foo.c:21:6: warning: 'b[0]' may be used uninitialized in this function [-Wmaybe-uninitialized]
   21 |  int max=b[0];
      |      ^~~

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