foo.c: In function 'main':
foo.c:8:5: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d",&n);//getchar?
     ^~~~~~~~~~~~~~
foo.c: In function 'hello':
foo.c:16:9: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d",&a[i]);//换行不空格可以吗
         ^~~~~~~~~~~~~~~~~

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