foo.cc: In function 'int main()':
foo.cc:7:29: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    7 |  for(int i=1;i<=n;i++) scanf("%lld",&a[i]);
      |                        ~~~~~^~~~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务