Santa was doing experiment with cockroach, first he cut it's one leg and told WALK. WALK. Cockroach walked. Then he cut it's second leg and told the same.
Cockroach walked. Then cut the third leg and did the same. At last he cut it's fourth leg and ordered it walk! But cockroach didn't walk.
Suddenly Santa said loudly, "I found it. If we cut cockroach's four legs, it becomes deaf.