I can't recall where I've seen this before, but it's http://mathworld.wolfram.com/SultansDowryProblem.html http://mathworld.wolfram.com/SultansDowryProblem.html

I can't recall where I've seen this before, but it's http://mathworld.wolfram.com/SultansDowryProblem.html http://mathworld.wolfram.com/SultansDowryProblem.html, the Sultan's Daughter problem.