The Beatles have a concert that starts in 17 minutes and they must all cross a bridge to get there. All four men begin on the same side of the bridge. It is nightfall, and there is only one flashlight. A maximum of two people can cross at one time. Any party who crosses, either 1 or 2 people, must have the flashlight with them, and the flashlight must be walked back and forth. Each band member walks at a different speed. A pair must walk together at the rate of the slower man's pace:

*Ringo: - 1 minute crossing
*George: - 2 minutes crossing
*Paul:- 5 minutes crossing
*John: - 10 minutes crossing

Example: If Ringo and John go first, 10 minutes have elapsed when they get to the other side of the bridge. If John then returns with the flashlight, a total of 20 minutes have passed and they have missed the concert.

There are two known answers to this problem.