A man from Switzerland is stuck in Germany during the World War II.
The only way to escape is to cross a bridge over a river from Germany to Switzerland.
There is a sentry beside the bridge who comes out every three minutes.
If the man goes from Germany to Switzerland, he will be shot.
If he wants to go from Switzerland to Germany, he will be taken back to Switzerland.
It takes six minutes to walks & four minutes if he runs.
How does the man escape?