foo.cc: In function 'int main()':
foo.cc:60:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   60 |     scanf(" %lld",&ar[i]);ar[i]%=10;ar[i+n]=ar[i];
      |     ~~~~~^~~~~~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务