answer.code: In member function ‘int Tree2::update(int, int, int, int, int)’:
answer.code:95:13: error: return-statement with no value, in function returning ‘int’ [-fpermissive]
   95 |             return;
      |             ^~~~~~
answer.code: In function ‘int query(int, int)’:
answer.code:165:1: warning: no return statement in function returning non-void [-Wreturn-type]
  165 | }
      | ^
answer.code: In member function ‘int Tree2::update(int, int, int, int, int)’:
answer.code:103:16: warning: control reaches end of non-void function [-Wreturn-type]
  103 |         push_up(k);
      |         ~~~~~~~^~~