4 sajhaist are crossing a Jholungwe Pul (bridge). It is night, total dark, so they need torch light to cross the Pul. The Pul is climsy, so only 2 people can cross simultaneously, and the group has only one flashlight. Everyone takes different time to cross it:
NSA crosses the bridge in 1 minute,
Punter crosses the bridge in 2 minutes,
HamroSajha crosses the bridge in 5 minutes,
HelpJava11 crosses the bridge in 10 minutes. ( im the slowest)

The bridge is going down in 17 minutes. How did they cross it within 17 minutes?