foo.c: In function 'main':
foo.c:18:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   18 |  scanf("%s",s1);
      |  ^~~~~~~~~~~~~~
foo.c:19:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   19 |  scanf("%s",s2);
      |  ^~~~~~~~~~~~~~

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