foo.c: In function 'main':
foo.c:10:10: warning: unused variable 'j' [-Wunused-variable]
    int i,j;
          ^
foo.c:6:4: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d",&n);
    ^~~~~~~~~~~~~~
foo.c:14:5: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d",&a[i]);
     ^~~~~~~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务