foo.c: In function 'sum':
foo.c:8:1: warning: control reaches end of non-void function [-Wreturn-type]
    8 | }
      | ^
foo.c: In function 'main':
foo.c:13:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   13 |  scanf("%d",&xmin);
      |  ^~~~~~~~~~~~~~~~~
foo.c:15:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   15 |  scanf("%d",&xmax);
      |  ^~~~~~~~~~~~~~~~~

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