foo.cc: In function 'int main()':
foo.cc:29:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   29 |     scanf("%s%d",a+1,&k);
      |     ~~~~~^~~~~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务