foo.c: In function 'main':
foo.c:19:3: warning: implicit declaration of function 'exit' [-Wimplicit-function-declaration]
   19 |   exit(1);
      |   ^~~~
foo.c:19:3: warning: incompatible implicit declaration of built-in function 'exit'
foo.c:2:1: note: include '<stdlib.h>' or provide a declaration of 'exit'
    1 | #include <stdio.h>
  +++ |+#include <stdlib.h>
    2 | int pd(int year)
foo.c:15:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   15 |  scanf("%d %d %d",&year,&month,&day);
      |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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