>A prisoner of war manages to escape from his prison, and must now cross the border, to get back to his own country. Specifically, he must cross a bridge across a river. He has the following information:
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A guard watches the bridge. However, the guard doesn't watch all the time; he only gets out of his building once every 7 minutes, to look at the bridge.
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However, it would take the prisoner 10 minutes to cross the bridge at top speed.
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The guard's role is to avoid people coming into, and getting out of, the country. People who try to come into the country are sent back. People who try to get out of the country, however, are shot.
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>How can our hero get out of the country?

He can run across the bridge and at the 7 minute mark turn around and it looks like he is trying to get into the country he just came from. The guard, will send him back to the wrong country.