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Problem C
Champagne Overflow

/problems/champagneoverflow/file/statement/en/img-0001.jpg
Image: Kenichi Nobusue; CC-BY 2.0.

A champagne pyramid is an arrangement of coupes (shallow glasses) used for festive occasions such as wedding receptions or New Year’s celebrations. The construction is based on the fact that a coupe can be placed on top of four others coupes, arranged in a symmetric fashion such that liquid overflowing from the top coupe is distributed equally among the four coupes below it.

Below is the champagne pyramid of height $3$ after champagne corresponding to $5$ coupes has been poured into the topmost coupe. It has overflowed and exactly filled all coupes on the middle level as well.

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Liquid overflowing from the bottom-most coupes – those on the table – is wasted. The construction can be iterated, leading to splendid towers of dizzying height. As of $2022$, the highest documented champagne tower consisted of more than fifty-thousand coupes.

In an ideal world, where every overflowing coupe distributes its liquid equally among its four supporting coupes, how much champagne is wasted when filling a champagne pyramid of given height from the topmost coupe?

Input

The height of the pyramid as a single integer $h$ with $1\leq h \leq 55$ (measured in coupe heights).

Output

A single integer: The amount of champagne (measured in coupes) that is wasted when filling all coupes by pouring champagne only into the topmost coupe.

Sample Input 1 Sample Output 1
1
0
Sample Input 2 Sample Output 2
2
0
Sample Input 3 Sample Output 3
3
7

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