foo.cc: In function 'int dfs2(int)':
foo.cc:53:1: warning: no return statement in function returning non-void [-Wreturn-type]
   53 | }
      | ^
foo.cc: In function 'int dfs(int, int)':
foo.cc:43:1: warning: control reaches end of non-void function [-Wreturn-type]
   43 | }
      | ^

[Hydro](https://hydro.ac)提供评测服务