foo.c: In function 'gys':
foo.c:14:1: warning: control reaches end of non-void function [-Wreturn-type]
   14 | }int main()
      | ^
foo.c: In function 'main':
foo.c:17:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   17 |  scanf("%d%d", &a, &b);
      |  ^~~~~~~~~~~~~~~~~~~~~
foo.c:19:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   19 |  scanf("%d%d", &c, &d);
      |  ^~~~~~~~~~~~~~~~~~~~~

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