an Indian chief had his three squaws sleeping on animal hides in his tepee. The first squaw slept on a cow hide, the second squaw slept on a horse hide, and the third squaw slept on a hippopotamus hide. Bye and bye, they all became pregnant and presented the chief with his heirs. The squaw who slept on the cow hide had a son, the squaw who slept on the horse hide had a son, but the squaw who slept on the hippopotamus hide had twin sons...
So the squaw of the hippopotamus is equal to the sons of the squaws of the other two hides