foo.c: In function 'main':
foo.c:9:2: warning: implicit declaration of function 'date' [-Wimplicit-function-declaration]
  date(n, m1, d1, m, m2, d2);
  ^~~~
foo.c:5:6: warning: unused variable 'sum' [-Wunused-variable]
  int sum;
      ^~~
foo.c:6:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %d %d", &n, &m1, &d1);
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.c:7:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %d %d", &m, &m2, &d2);
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.c: In function 'date':
foo.c:50:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^

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