foo.c: In function 'main':
foo.c:6:13: warning: format '%d' expects a matching 'int *' argument [-Wformat=]
   scanf("%d%d%d",&a[i]);
            ~^
foo.c:6:15: warning: format '%d' expects a matching 'int *' argument [-Wformat=]
   scanf("%d%d%d",&a[i]);
              ~^
foo.c:6:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d%d",&a[i]);
   ^~~~~~~~~~~~~~~~~~~~~

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