foo.c: In function 'main':
foo.c:9:10: warning: unused variable 'k' [-Wunused-variable]
  char n, k;
          ^
foo.c:9:7: warning: unused variable 'n' [-Wunused-variable]
  char n, k;
       ^
foo.c:10:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &year);
  ^~~~~~~~~~~~~~~~~~
foo.c:12:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &month);
  ^~~~~~~~~~~~~~~~~~~
foo.c:14:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &day);
  ^~~~~~~~~~~~~~~~~

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