/in/foo.cc: In function 'void dfs(int, int)':
/in/foo.cc:23:16: warning: iteration 4 invokes undefined behavior [-Waggressive-loop-optimizations]
   int xx=x+dx[i];
            ~~~~^
/in/foo.cc:21:15: note: within this loop
  for(int i=1;i<=5;++i)
              ~^~~