Hi,
There are 4 people that want to cross the bridge. They have 1 flash light.

Person A takes 10 minuts to cross the bridge,
Person B - 5 min,
Person C - 2 min,
Person D - 1 min

The bridge can only hold 2 people at a time at most.
They can only cross with a flash light.

How can they ALL cross the bridge in 17 minutes?