/in/foo.cc: In function 'int find(int, int)':
/in/foo.cc:21:16: warning: iteration 3 invokes undefined behavior [-Waggressive-loop-optimizations]
   int ty=y+dy[i];
            ~~~~^
/in/foo.cc:18:15: note: within this loop
  for(int i=0;i<4;i++)
              ~^~