Score : $100$ points

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 $f(N)=X$.

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