You are given an equilateral triangle. An iteration consists of taking every edge in the current figure and, if possible, using it as base for a new equilateral triangle.
Your task is to find the perimeter of the figure at iteration N.
Input
A single integer: N.
Output
A single integer: the perimeter of the figure.
Constraints
- 1 ≤ N ≤ 109
Samples
| Input | Output |
|---|---|
| 1 | 3 |
| 4 | 15 |
| 10 | 42 |
