A mathematical puzzle that baffled the top minds in the field of symbolic dynamics for nearly four decades has been cracked -- by a 63-year-old immigrant who once had to work as a security guard.

Avraham Trahtman solved the elusive "Road Coloring Problem" posed in 1970. The conjecture assumed that it's possible to create a "universal map" that can direct people to arrive at a destination, at the same time, regardless of starting point.

Over the years, some 100 scientists attempted to solve it. All failed, until Trahtman jotted down the solution last year in eight short pages. "The solution is not that complicated. It's hard, but it is not that complicated," he said. "Some people think they need to be complicated. I think they need to be nice and simple."

Stuart Margolis, who recruited Trahtman -- who immigrated to Israel from Russia at age 48 -- to teach at Bar Ilan University near Tel Aviv, called the solution one of the "beautiful results."

"Math is usually a younger person's game," he said. "Usually you do your better work in your mid-20s and early 30s. He certainly came up with a good one at age 63."

He said it could have many applications. "Say you've lost an e-mail and you want to get it back -- it would be guaranteed," he said. "Let's say you are lost in a town you have never been in before and you have to get to a friend's house and there are no street signs -- the directions will work no matter what."

To see the solution, www.startribune.com/a4173.