The dragon of ignorance has three heads and three tails. However, you can slay it with the sword of knowledge by cutting off all its heads and tails. With one swipe of the sword you can cut off one head, two heads, one tail, or two tails.
But . . .
When you cut off one head, a new one grows in its place.
When you cut off one tail, two new tails replace it.
When you cut off two tails, one new head grows.
When you chop off two heads, nothing grows.
Help the world by slaying the dragon of ignorance.
How did you get the answer? Here is my solution: Sword of Knowledge - Solution