foo.cc: In function ‘int dfs(int, int, int, int)’:
foo.cc:24:1: warning: no return statement in function returning non-void [-Wreturn-type]
   24 | }
      | ^
foo.cc:7:5: warning: infinite recursion detected [-Winfinite-recursion]
    7 | int dfs(int sx,int sy,int fx,int fy)
      |     ^~~
foo.cc:18:28: note: recursive call
   18 |                         dfs(nx,ny,fx,fy);
      |                         ~~~^~~~~~~~~~~~~