foo.cc: In function 'int main()':
foo.cc:37:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%s", a+1);
 ~~~~~^~~~~~~~~~~
foo.cc:38:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%s", b+1);
 ~~~~~^~~~~~~~~~~

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