foo.cc: In function 'int main()':
foo.cc:13:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   13 |     scanf("%d%d%d%d", &l, &s, &t, &m);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:14:23: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   14 |     For(i, 1, m) scanf("%d", &a[i]);
      |                  ~~~~~^~~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务