The Bridge and Flashlight Puzzle

This is very popular puzzle and most of you would have already encountered it. There are 4 men who want to cross a bridge. They all begin on the same side.You have to get all of them across to the other side in shortest time. It is night. 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. The flashlight must be walked back and forth, it cannot be thrown etc. Each man walks at a different speed. A pair must walk together at a rate of the slower man's pace. Man 1: 1 minute to cross. Man 2: 2 minutes to cross. Man 3: 5 minutes to cross. Man 4: 10 minutes to cross. For example, if Man 1 and Man 4 walk across first, 10 minutes have elapsed when they get to the other side of the bridge. If Man 4 returns with the flashlight, a total of 20 minutes have passed. So what is the shortest time and what is the sequence ?