You are at a shooting range. You have $N$ target labeled from $1$ to $N$ from left to right.

Your task is to shoot the target by performing the following operation.

In each round starting from the first element and moving from left to right, shoot every alternate target.

Repeat the above step until only one target is left.

By shooting a target labeled i you will get i points.

Task

Return the total number of points you will get by shooting targets until only one target is left.

Example

Assumption

$N=7$

Approach

Targets $=[1,2,3,4,5,6,7]$

Initial points $=0$

Targets $=[1,2,3,4,5,6,7].$ Targets to be removed are $1,3,5,7.$ Points $=0+1+3+5+7=16.$

Targets $=[2,4,6].$ Targets to be removed are $2,6.$ Points $=16+2+6=24.$

Targets $=[4],$ only one target is left therefore return total points i$.$e$.24.$