The Crossing Bridge-brain teaser

Riddle 
Four people need to cross a bridge at night. They only have one torch, and the bridge is too dangerous to cross without it. The bridge can only hold two people at a time. The four people take different times to cross: 1 minute, 2 minutes, 7 minutes, and 10 minutes. How do they all get across in the shortest time possible?

    1. The 1-minute and 2-minute people cross first with the torch (2 minutes). 2. The 1-minute person goes back with the torch (1 minute). 3. The 7-minute and 10-minute people cross with the torch (10 minutes). 4. The 2-minute person goes back with the torch (2 minutes). 5. The 1-minute and 2-minute people cross again (2 minutes). Total time: 17 minutes.