foo.c: In function 'main':
foo.c:11:15: warning: variable 'len' set but not used [-Wunused-but-set-variable]
  int n, k, i, len, max;
               ^~~
foo.c:18:4: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d",&a[i]);
    ^~~~~~~~~~~~~~~~~
foo.c:20:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&k);
   ^~~~~~~~~~~~~~

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