foo.cc: In function 'int main()':
foo.cc:48:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   48 |     scanf("%d%d", &l, &r);
      |     ~~~~~^~~~~~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务