A laboratory is testing a new prototype of a "highly elastic" ball. The experiment begins by dropping the ball from a starting height of N meters above a flat surface.
The ball follows a predictable physical property: every time it impacts the ground, it rebounds to a height exactly equal to 50\% of the height from which it last fell. The ball then falls back to the ground from that peak height to complete the bounce, and same process continues forever.
The researchers are interested in the total distance the ball travels (the sum of all vertical movement, both upward and downward) by the moment it touches the ground for the 10^{18}-th time.
Input
The only line of the input contains a single integer N (1 \le N \le 10^{15}), the initial height from which the ball was dropped.
Output
Print a single integer — the total distance traveled by the ball.
Your answer will be considered correct if its absolute or relative error does not exceed 10^{-6}.
Any standard notation (including scientific) is acceptable.
Examples
| standard input | standard output |
|---|
| 2
| 6
|