Bridge n Torch

Bridge -- Torch

PROBLEM :
Crossing the bridge

Write a program to print the minimum time taken to get N people from one side of a bridge to the other if

a)The bridge can only hold two people at a time.

b)It's dark and the only flashlight must be carried while crossing.

c)People are numbered from 1 to N. The k-th person takes k seconds to cross the bridge.

d) A pair crosses at the speed of the slowest member.

For example:
Input: 4
Output: 11

i.e
1-3 cross(3), 1 returns(1)
1-4 cross(4), 1 returns(1)
1-2 cross(2)
SUM : 3 + 1 + 4 + 1 + 2 = 11