foo.c: In function 'main':
foo.c:20:11: warning: format '%d' expects a matching 'int' argument [-Wformat=]
  printf("%d\n%ld\n");
          ~^
foo.c:20:16: warning: format '%ld' expects a matching 'long int' argument [-Wformat=]
  printf("%d\n%ld\n");
              ~~^
foo.c:7:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%ld%ld", &a, &b);
  ^~~~~~~~~~~~~~~~~~~~~~~

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。