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 ≤ 10`^{9}

### Samples

Input | Output |
---|---|

1 | 3 |

4 | 15 |

10 | 42 |