Please help this family to cross to the other side of the bridge.
Notice that: It is night . There is 1 lamp .
A maximum of 2 persons can cross at one time, and they
must have the lamp with them.
Each person walks at a different speed: 1sec 3sec 6sec 8sec 12sec.
A pair must walk together at the rate of the slower person.
The lamp enough for 30 sec only!!!

