foo.c:17:1: warning: return type defaults to 'int' [-Wimplicit-int]
   17 | main()
      | ^~~~
foo.c: In function 'main':
foo.c:19:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   19 |  scanf("%d%d\n",&b1,&a1);
      |  ^~~~~~~~~~~~~~~~~~~~~~~
foo.c:20:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   20 |  scanf("%d%d",&b2,&a2);
      |  ^~~~~~~~~~~~~~~~~~~~~

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