foo.cc: In function 'void splay(int, int, int)':
foo.cc:40:20: warning: suggest explicit braces to avoid ambiguous 'else' [-Wdangling-else]
   40 |                 if (z)
      |                    ^
foo.cc: In function 'void build(int, int, int)':
foo.cc:112:21: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
  112 |         int mid = l + r >> 1;
      |                   ~~^~~

[Hydro](https://hydro.ac)提供评测服务