Problem Statement

We have a cord whose length is a positive integer. We will perform the following condition until the length of the cord becomes at most ~2~ :

• Operation: Cut the rope at two positions to obtain three cords, each with a length of a positive integer. Among these, discard one with the longest length and one with the shortest length, and keep the remaining one.

Let ~f(N)~ be the maximum possible number of times to perform this operation, starting with a cord with the length ~N~ .

You are given a positive integer ~X~ . Find the maximum integer ~N~ such that ~f(N)=X~ .

Constraints

• ~1 \leq X \leq 40~

Input

The input is given from Standard Input in the following format:

~X~

Output

Print the value of the maximum integer ~N~ such that ~f(N)=X~ .

Sample Input 1

2

Sample Output 1

14