Limits
1s, 512 MB

From the above figure, the number of nodes for the first three depths are 3, 9, and 27.

You will be given a number N. Your task is to find out the total number of nodes within the first N depth.

Enter a single integer, N, where 0 ≤ N ≤ 30.

Print the answer for the mentioned problem.

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

2 | 13 |

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

3 | 40 |