/in/foo.cc: In function 'int dfs(int, int)':
/in/foo.cc:21:1: warning: no return statement in function returning non-void [-Wreturn-type]
 }
 ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:38:26: warning: 'start_y' may be used uninitialized in this function [-Wmaybe-uninitialized]
     dfs(start_x, start_y);
                          ^
/in/foo.cc:38:26: warning: 'start_x' may be used uninitialized in this function [-Wmaybe-uninitialized]